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Troubled Houses - The Home Owner's Resourcesm - Heat & AC

We see many interesting adverse conditions during our inspections, partly because of the unlimited number of ways people can mess up a house, but also because we do a thorough inspection to reveal these adverse conditions. We hope these stories and illustrations help home owners avoid these costly conditions by learning about causes, preventions, and remedies. A home purchase can create opportunities for the new owner to improve the home, possibly increasing its value, durability, and usefulness.

NOTICE TO BUYERS & SELLERS: This site does NOT encourage or discourage the purchase of any individual house, or style, age, location, or condition of house.  Conditions shown and/or described in the following articles may have been remedied at the house where these conditions were found.  These conditions typically can be remedied by qualified contractors. The presence of these conditions in any house is comparable to any other real estate consideration such as price, size, or location.  Consult a qualified home inspector before purchasing any house, and consult a qualified real estate agent for more information on how to handle a real estate transaction where adverse conditions are reported in a home inspection.   This site does not describe any house by address or knowingly show a readily identifiable exterior image.  Further, no home actively listed for sale  will be described on these pages at the time the article is posted.

Copyright 2014 All rights reserved.  "Troubled Houses - The Home Owner's Resource" is a SERVICE MARK of Hankey & Brown Inspection Service Inc.
                                          IMPORTANT NEWS for home owners with central air conditioners built BEFORE 2010.
Your air conditioner refrigerant is probably HCFC-22 also known as R-22. This product is in short supply and will not be produced or imported into the United States after the end of 2019 since it is an ozone depleting substance. 

You can determine if your air conditioner uses R-22 by reading the label on the outdoor unit of our central air conditioner. If it says R-22 or HCFC-22 we recommend you have the equipment serviced THIS SUMMER. R-22 is expensive now, but will be more expensive next year. If your air conditioner malfunctions, it may not be worth repairing. 

For more information see a list of frequently asked questions from the US EPA

 List of topics and all articles in this resource. 

THANK YOU for visiting   Learn more about our services, which now include IR Thermography, radon testing, and carbon monoxide tests.

Heating, Ventilation, and Air Conditioning (HVAC) story list
    Improper air ducts reduce comfort
    Why we open the attic hatch. (Broken vent)     
    Attic inspections are necessary
    Chimney Cap Comparison  
    Furnace inspections are critical (damaged heat exchanger)
    Frosted (deteriorated) siding (reversed vent terminal)
Warm but with the potential to poison (boiler leaking fumes)
   Permitted, installed, but NOT inspected (poor workmanship)
    The Unintended Humidifier (Condensate leaks)
   Undisclosed Buried Oil Tank
    Gas fired equipment should not make soot!
(Gas fireplace)
   Drywall dust hurts heating and cooling equipment!
    Use the recommended furnace filter!  
    More on furnace filters & link to great website Carbon monoxide myths.
    Clean the air intake on your heat recovery ventilator
    Don't rely on inspections done for others!
Also see our Carbon Monoxide Tests page
    A rare, but potentially serious furnace maintenance issue (reversed cover panels)

   Permitted, Installed, but NOT inspected! Incomplete and incorrect workmanship

Early in 2014 we inspected the furnace shown
at right.  The serial number was consistent with a 2009 model, but we found no label or tag with an install date or installer's name.

Four adverse conditions in the HVAC system are shown in the photo at right: 

1. The filter opening at the bottom right side of the furnace is uncovered.
2. The white air grill in the return air plenum to the right of the furnace should not be present. This opening reduces return air circulation in the upper floors, reduciing the effectiveness of the central air conditioner.
3. The blue device above the return air grill is a drum humidifier.  These are not recommended because the drum shaped sponge that transfers moisture to the air rotates in a reservoir of water.  The reservoir and sponge often become covered with mold.
4. No sealant has been applied to the supply air penetrations for the AC lines or AC drain.

(C) 2014 Poorly installed furnace with 4 adverse conditions, including register in return air plenum.  ASHI Certified Inspectors, Winter Park, CO


 Unsealed penetrations of a furnace supply air plenum . (C) 2014, ASHI Certified Inspectors, Winter Park, CO
The unsealed penetrations for the refrigerant lines (top) and the condensate drain (bottom) permit supply air to escape, overheating or over cooling the area near the furnace.

Uncovered furnace filter slot. (C) 2014, ASHI Certified Inspectors, Winter Park, CO
The uncovered filter slot further reduces the return air flow at upper floors and permits unfiltered air to reach the coils of the furnace and air conditioner.



Drum humidifier on a furnace. (C) 2014, ASHI Certified Inspectors, Winter Park, CO
This drum humidifier is similar to the cut away
shown at right. It has a high potential to grow mold on the drum and in the pan.

Drum humidifier drawing from Carson Dunlop Illustrated Home


A check of the city records for this property found that a permit was issued for intallation of this furnace in November of 2009, but that three attempts to inspect the furnace in 2011 failed and it was not listed as approved. This could explain why we found these conditions in early 2014.  We recommended these conditions be corrected by a qualified HVAC firm and that a final inspection by the city confirm a proper installation.  

Improper air ducts reduce comfort in a heating-cooling system 

 Return air duct formed in joist space lacks an end panel. (C) 2010, ASHI Certified Inspectors, Winter Park, CO        Combustion air duct directly connected to furnace blower cabinet.  Troubled house photo (C) 2010, ASHI Certified Inspectors, Winter Park, CO

Forced air heating & cooling systems include both supply and return air ducts.  A large blower in the furnace moves air into the furnace via "return" ducts which have negative air pressure (suction) and out of the furnace via "supply" ducts.  The return air ducts must be tight to establish good suction at the return air grills in the various rooms.  The photos above show two of several problems with the return air system on this 1992 built home.   The left photo is of a return air duct in the unfinished area near the furnace.  The part of the return air duct was created by installing a sheet metal "pan" on the bottom of the floor joists.  Unfortunately the installer forgot to install an end cap in this return, so this return is not conveying suction (negative or return air flow) to the return grill on the room above. 

The right photo shows that the combustion air duct (black tube) is directly connected to the furnace blower cabinet.  Each time the furnace blower runs, air is drawn in directly from outdoors, whether the house needs extra air or not.   Installations similar to this (combustion air direct connected to the return air duct, not the blower cabinet) were commonly used in the 1970's and 80's.  Good practice today is to simply bring the combustion air duct to the furnace room as a passive air supply (shown below). This prevents the blower from pulling unconditioned air (hot, cold, damp or dry) directly into the furnace  by this air duct, whether the house needs extra air or not.   The passive duct allows air to enter when the air pressure in the house is lower than air pressure outdoors.  This can occur when exhaust fans, dryers, or the furnace or water heater are in use. 

                     Outside air supply drawing from Carson Dunlop (Dearborn) Illustrated Home, with additional text by Roger Hankey, ASHI Certified Inspector in Winter Park, CO

In this case, we recommended both the return ducts and outside air supply be corrected by a qualified heating contractor to improve air circulation in the house and improve the efficiency of the system.  We also suggested replacement of the 17 year old furnace with a sealed combustion direct vent furnace to take advantage of the 30% Federal tax credit for energy efficiency improvements done by the end of 2010.   Return to story list. 

          Furnace inspections are critical (damaged heat exchanger)

Vent in furnace blower cabinet in 50 yr old gas furnace (C) 2010 ASHI Certified Inspectors, Winter Park, CO

A careful furnace inspection is necessary to identify potentially dangerous conditions. This 53 year old furnace had a cracked vent connection on its heat exchanger. (between A & B in the photo)  Replacement was recommended since this crack was on the suction side of the blower (see inset image) which could pull combustion fumes into the circulating air. (This furnace design was abandoned by manufacturer's more than 43 years ago.)  The furnace had been "certified" by a reputable heating company only 5 days prior to our inspection.  The company rechecked the furnace and agreed with our findings.  Our customer obtained a $3,500 price reduction from the seller to help cover the cost of a new furnace.

Frosted (deteriorated) siding

                                   Frosted moisture damaged fiber cement siding due to reversed vent terminal, Troubled House photo (C) 2010, ASHI Certified Inspectors, Winter Park, CO
This one year old house has cement fiber siding and a gas fired high efficiency furnace with a sidewall vent.  The vent pipe and air intake pipe are reversed in the terminal directing moisture onto the wall and causing  siding deterioration.  The terminal needs to be turned 180 degrees to direct the vent out the front opening instead of onto the siding. 

Detail of frosted moisture damaged fiber cement siding due to reversed vent terminal, Troubled House photo (C) 2010, ASHI Certified Inspectors, Winter Park, CO    install manual

Warm but with the potential to poison

80 year old residential boiler, designed for coal, gas conversion burner, Troubled Houses  Photo (C) 2010 ASHI Certified Inspectors, Winter Park, CO

This 80 year old boiler was designed to burn coal, then converted with a gas burner over 43 years ago.  Of course it is very inefficient, but worse yet it has not had regular maintenance and has many unsealed gaps and joints (one shown below) that leak combustion fumes into the building.

Unsealed gap at old boiler cleanout door on 80 year old residential boiler, designed for coal, gas conversion burner, Troubled Houses  Photo (C) 2010 ASHI Certified Inspectors, Winter Park, CO

We recommended boiler replacement for efficiency, reliability, and to reduce the potential for carbon monoxide leakage.  If the boilers are to remain in use, we recommend having a qualified technician seal all the holes, gaps, joints, etc.   Click here to learn more about our services.   Return to story list.

                                            The Unintended Humidifier

     Furnace with condensate leak. Troubled Houses photo (C) 2010 ASHI Certified Inspectors, Winter Park, CO


This modern high efficiency furnace is classed Category IV (condensing type) which means its vent temperatures are so cool (about 200ºF) that considerable amounts of water must be drained from the secondary heat exchanger and vent.  Unfortunately this furnace has one or more condensate leaks in the hoses and fittings which are intended to convey the liquid condensate (slightly acidic water) to the nearby floor drain. 

                                          Detail of furnace condensate leak. Troubled Houses photo (C) 2010 ASHI Certified Inspectors, Winter Park, CO

This kinked hose is one of at least two places where the condensate is leaking out of the furnace and into the blower cabinet.  Note the extensive corrosion due to the acidic condensate spill.  This is a common problem with this type of furnace.  Annual service is recommended to catch these conditions before the furnace is damaged.

                                       Loose rusty blower cabinet bottom in furnace condensate leak. Troubled Houses photo (C) 2010 ASHI Certified Inspectors, Winter Park, CO

The furnace blower cabinet and its insulation are wet.  The metal is rusty and the insulation has a high potential for mold growth.   Another common adverse condition is the installer's failure to secure and seal the bottom panel of the furnace blower cabinet.  Presently the furnace draws some air through this loose panel whenever the blower runs, reducing the effectiveness of both heating and cooling.  Our inspection report identified these conditions and recommended correction by a qualified heating technician.

Undisclosed Buried Oil Tank

Buried Oil Tank Fill pipe cap Troubled Houses (C)  ASHI Certified Inspectors in Winter Park, CO

The seller of this "Prairie School" architect designed home near a city lake was unaware they had an abandoned buried oil tank.  Our inspection saved the buyer the $3500 tank sealing costs.   Click here to see what our customers say about our service.      

Chimney Cap Comparison

Chimney cap comparison Troubled Houses (C) , ASHI Certified Inspectors in Winter Park, CO

The chimney on the left has had its cap replaced with a concrete cap which sheds water. The chimney on the right has its original mortar cap (a typical mortar crown) which lets water run down the side of the chimney.  This has lead to freeze - thaw damage to at least six bricks on the visible side of the chimney.  This chimney would benefit from brick repair AND a new cap to prevent further freeze thaw damage.   Our inspections include roof & chimney when readily accessible. Click here for more information.

Why we open the attic hatch. (Broken vent)

We occasionally get some resistance from real estate agents and home owners about opening an attic hatch that has its original spray texture or drywall joint cement coating.  These hatches are installed to permit the attic to be insulated and for service work such as cable installations, etc., as well as inspections.  These hatches are not "sealed" and typically can be opened with simple upward hand pressure.  When carefully opened and reclosed, there is almost no sign that the hatch was even disturbed. 

If the ceiling finish on the hatch is completely intact, it is unlikely anyone has viewed the attic since the house was built.  There are a wide variety of adverse conditions that might be present in the attic, and can ONLY be discovered by an attic inspection. 

This six year old townhouse has a metal vent for the furnace and water heater which extends about 3 feet above the roof.  When viewed from the exterior, the vent looks completely normal.  The attic hatch had not been opened.
  (C) 2014, Furnace vent above a townhouse roof.  ASHI Certified Inspectors, Winter Park, CO
A view of the vent from the attic hatch shows the vent in the far corner of the attic, rising up and out near the top of the attic.  There is a slight indication of an abnormality at the 45º elbow near the roof penetration.  A closer look, obtained by crawling across the roof trusses and verified by inserting a folding rule into a gap in the vent, reveals the vent has separated at a joint in the elbow. 

            (C) 2014 HankeyandBrown.comMetal vent for gas equipment viewed from attic hatch. Photo by ASHI Certified Home Inspector Roger Hankey, Winter Park, CO     (C) 2010 Broken B vent for gas equipment detail view. Photo by ASHI Certified Home Inspector Roger Hankey, Winter Park, CO

This broken elbow can permit the products of gas combustion, carbon dioxide and water vapor, to enter the attic.  Left undiscovered, winter operation of the furnace vent would discharge a large amount of water vapor into the cold attic where it would condense on the roof sheathing.  Conditions such as this have caused extensive water damage in other cases.  A prompt repair of the broken vent elbow, by a qualified HVAC firm, was recommended.  We contacted the management of the townhouse owners association and recommended attic inspections of other units in the townhouse complex.  Potential causes for the break in the elbow are impact with the exterior portion of the vent due from activities such as reroofing, or use of the sheet metal angle brackets on the underside of the roof.  These brackets may restrict the movement of the vent as it expands and contracts from heating and cooling, causing the vent to pull itself apart at the elbow joint. 

Return to story list.

Gas fired equipment should not make soot!

         Sooty siding and vent terminal below an elevated porch. Troubled Houses (C) 2011 ASHI Certified Inspectors, Winter Park, CO
The metal box on the wall below this elevated porch is the vent terminal for a direct vent gas fireplace of a 1990 built home in Chanhassen, CO.  Notice the blackened area on the box and darken siding above the vent terminal.  This area is shown in detail below.

              Sooty vent terminal for a gas fired direct vent fireplace. (C) 2011 ASHI Certified Inspectors, Winter Park, CO
The black deposits on the vent terminal and siding are soot, a form of carbon that is a classic sign of poor combustion. (Often due to insufficient combustion air).  This is true of ALL gas fired equipment from a kitchen stove to a furnace.  Soot should not be present in the combustion chamber or on the vent.  The equipment should also NOT be making any odor (although a gas furnace or gas fireplace may occasionally create a slight odor of toasted dust when operated after a long period of non-use.  The carbon monoxide reading in the vent was over 41 0 ppm. (Under 100 ppm would be normal).  The recommendation in this case was to have the fireplace serviced as soon as possible by a qualified gas fireplace technician and tested for carbon monoxide.

Attic inspections are necessary

A thorough home inspection involves examining ALL readily accessible areas of the house, AND mentally connecting the conditions found in one area with the condition of related components located elsewhere in the house.  This is particularly true of a heating system which often has components such as a chimney that extend from the foundation to above the roof.  Often, when conditions are found in multiple areas, the experienced inspector will relate these individual observations to the overall performance of the system.  The chimney of this 99 year old St. Paul home is a good example.  

Brick chimney with loose mortar (C) 2012 Roger Hankey ASHI Certified Inspector, Winter Park, CO Detail of brick chimney with loose mortar (C) 2012 Roger Hankey ASHI Certified Inspector, Winter Park, CO
Notice that there are gaps in the mortar in the top 3 courses, and that there is no metal liner rising above the top of the chimney.  Our inspection of the 49 year old gas fired boiler revealed that it vented into the clay tile of this chimney AND that it was leaking carbon monoxide out around the boiler shell.
 Carbon monoxide test of 49 year old gas fired boiler (C) 2012 Roger Hankey ASHI Certified Inspector, Winter Park, CO
The City of St. Paul Truth in Sale of Housing report indicated that the attic was all finished rooms with no attic access, but this was not the case.  We found and opened a hatch to the attic above the 3rd fl. rooms and found two conditions not listed in the city report.


Damage to brick chimney in attic due to lack of a metal liner for gas fired boiler (C) 2012 Roger Hankey ASHI Certified Inspector, Winter Park, CO  Recessed light in attic leaking air from house to attic due to lack of an air tight cover. (C) 2012 Roger Hankey ASHI Certified Inspector, Winter Park, CO
The photo at the left shows the deterioration of the attic section of the chimney.  This was caused by condensation of the boiler vent gases within the chimney due to the lack of a metal liner in the flue.  49 years of slightly acidic condensate leaked through the joint in the clay tile liner and deteriorated the mortar to the point where a brick broke loose from the side of the chimney.  We also found that the recessed lights installed in the 3rd floor ceiling did not have air tight covers and were leaking warm indoor air into the attic.  We advised installation of a metal flue liner for the boiler, service or replace the boiler to correct the carbon monoxide leakage, chimney repair, and installation of air tight insulated boxes over the recessed lights. 


We recommend that home buyers do NOT rely solely on required municipal Truth in Sale and Time of Sale evaluation reports.  These reports are NOT the same as an inspection done to the ASHI® Standard of Practice home inspection.  Also see: Don't rely on inspections done for others. 


Forced air heating systems are not intended to be used during construction. This is particularly true during the sanding of the gypsum wallboard joints. We have recently encountered several homes where this recommendation was not followed. We have seen this in both new homes, and older homes where an area was remodeled and where new rooms were added.  UPDATE 1-30-2018  We have received confirmation that in CANADA new home builders have followed Canadian furnace manufacturer's requirement and are all using temporary heat for homes under construction. (per AtlasCare Heating & Cooling, Oakville, Ont.)  Unfortunately many US builders continue to ignore this issue.   To see more horror stories about duct in furnaces and ducts, click here.

  Drywall dust in a new furnace blower cabinet. (C) 2012 Roger Hankey ASHI Certified Inspector, Winter Park, CO
Gypsum wallboard dust is composed of very fine particles and this dust is almost pure white. It travels throughout the heating system and coats the blower, heat exchangers, cooling coils, ducts and continues to blow into the home whenever the blower operates.

                    White drywall dust on a new furnace blower. (C) 2012 Roger Hankey ASHI Certified Inspector, Winter Park, CO 
The dust is much more than a cosmetic problem. First, drywall dust is a known health risk. There are occupational regulations on the control of drywall dust. Further, and more important to the home owner, manufacturers of furnaces, air handlers, and coiling coils know that the drywall dust can cause corrosion on metallic surfaces of the heating equipment, and a layer of dust reduces the efficiency of heat transfer on the heating and cooling components. Most manufacturers do NOT recommend use of the furnace as a construction heater, and when the furnace is used, the installation instructions carry very specific instructions on how the furnace is to be used, maintained, and cleaned prior to regular use of the equipment. Failure to follow the instructions can void the warranty.
       Operating instructions for a new furnace. Roger Hankey ASHI Certified Inspector, Winter Park, CO
Most reputable builders do not use the furnace during construction and best practice is to seal off any heat registers and grills during drywall sanding so that the dust does not contaminate the heating and cooling system.

 White drywall dust in the return air plenum of a new furnace . (C) 2012 Roger Hankey ASHI Certified Inspector, Winter Park, CO

<- One way to check for drywall dust is to open the filter cover and look into the return air duct.  

      White drywall dust in an air duct of a new house . (C) 2012 Roger Hankey ASHI Certified Inspector, Winter Park, CO
Another way is to lift a supply air register and check inside the duct to that register.  In either case, if white dust is present, a professional cleaning of the entire system is recommended

A longer version of this article has just been published at Click here for the article.

                                            Use the recommended furnace filter.


The image at right shows that whoever installed the blue and white filter did not read the CAUTION label or deliberately chose to ignore the message on the label.  Worse yet, the 1" wide filter selected is a  costly filter and if left in place more than a month has a high potential for causing over heating damage to the furnace.  Four inch thick filters are recommended whenever the filter rack can accomodate that size filter.  Four inch thick filters can last six months to a year and do an excellent job of filtering out fine particles from the air.

(C) 2012 One inch furnace filter installed in a furnace with a CAUTION label indicating 1" filters should not be used.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO


 Clean the air intake on your heat recovery ventilator

Thousands of Minnesota homes built since 1985 have air to air heat exchangers, also known as heat recovery ventilators installed to improve indoor air quality. These devices drawn in fresh outdoor air while exhausting an equal volume of stale indoor air. The two air streams pass each other in a heat exchanger and the exhaust air gives up about two thirds of its heat to the incoming air. Hence, the name, heat recovery ventilator. See drawing below.

Unfortunately some of the maintenance tasks described in the drawing are overlooked or forgotten by a large majority of home owners.  This is particularly true of the task of checking and cleaning the air intake.  A typical air intake location is shown below.

 (C) 2013 Locaction of HRV air intake hood on rear of home  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO
A look into the hood reveals that the metal mesh over the intake is completely clogged with cottonwood tree fuzz and dust.
(C) 2013 Clogged HRV air intake hood.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO
When operating without intake air, the device becomes an exhaust only fan.  This can lead to numerous adverse consequences including elevated levels of moisture and radon, cold drafts, and higher heating costs.  Cleaning the screen is easy with a car windshield snow brush.  The key is to make a schedule to ensure that this screen is checked several times a year so that it can be kept clean.  

                 Don’t rely on inspections done for OTHERS.

The information provided in disclosure documents or inspections done for OTHERS can be incomplete, incorrect, false, or not intended to meet the needs of home buyers.  We recommend that home buyers obtain inspections done to meet their needs by vendors that respond directly to them.

Editor's Note:  This article was submitted to US Inspect, City of Minnetonka Inspections Dept., the heating contractor, and our customer, for comments prior to posting.  This article incorporates comments received from the heating contractor and the city inspections dept.
Inspection reports done for purposes other than pre-purchase often include statements that home buyers should not rely on those reports.  For example, the Worldwide Employee Relocation Council (ERC) Property Assessment has headlines and text which state:

    This document is a Property Assessment. It is not a buyer's home inspection.

This document should not be used in place of nor be mistaken for a general home inspection or specialty type inspection performed by a licensed or trades professional (e.g., professional home inspector, engineer, pest control operator, electrician, plumber, roofer or HVAC specialist, pool/spa specialist, etc.).

This Property Assessment was prepared exclusively and for the sole use of the Client identified below (the "Client") under an established business-to-business relationship for the specific purposes of assisting with the relocation of an employee. It is not intended for use, nor is it to be relied upon, by any party other than the Client, including, but not limited to, buyers, sellers, lenders, real estate brokers/agents, and/or appraisers.

The Client may be required to provide this Property Assessment to other parties in order to comply with disclosure obligations under applicable federal, state and/or local law(s); however, no disclosure of this Property Assessment to other parties, including prospective buyers, shall be deemed to create or give rise to a duty of care or performance on the part of the Property Assessment Provider identified below or the Client toward such OTHER (emphasis added) parties.

Accordingly, no party OTHER THAN THE CLIENT (emphasis added) may rely upon or be influenced by this Property Assessment when considering the property. The Property Assessment Provider prepared this Property Assessment in accordance with Client directives and based it on findings gathered at the property address identified below AND OTHER (emphasis added) property information sources. END OF QUOTE.

We recommend you obtain a copy of reports such as the ERC or other inspections and provide them to the inspector YOU hire.  The inspector will benefit from some of the basic information provided in the report and will be able to cross check the inspection findings.

We recently encountered an ERC report, done in September 2014, by US Inspect, a nationwide vendor of relocation inspections.

Our customer had forwarded us the ERC report which we reviewed prior to our inspection.   Starting on line 1 of the first section, the report was incomplete (no status rating for walkways).  The attic section had 3 unrated line items.  There were 2 unrated basement items. The electrical section had no rating on the smoke detector line. The heating section had 4 unmarked line items: thermostat, humidifier, draft control, and pressure relief valve.  Further, the furnace was listed as approximately 5 years old, when a check of the online city permit records showed the furnace was installed in April 2013.

We participated in the design of the ERC form, over 20 years ago, and know that every item is to be marked, since one of the ratings is “not present”.  ERC reports also include a set of photographs. Our review of the photos led us to believe that there might be unreported concerns in the attic.  Given the many unrated items and the unreported possible concerns in the attic photos, the customer hired us to do an inspection of most of the systems in the house. 

Our inspection revealed one main area of concern:
- the furnace vent was connected to a masonry chimney without a metal liner as required by the furnace manufacturer

(C) 2014 Furnace with test tag on duct.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO (C) 2014 Furnace installers manual.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO
     Furnace with test card on duct.           Furnace installation manual page 14


(C) 2014 Furnace installers test record.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO (C) 2014  Masonry chimney, tile flue, no liner.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO
   Furnace installers test card                                     Chimney flue serving furnace.

The furnace situation illustrates why home buyers should not rely on city permit inspections or heating contractors.  We found the installer’s test tag proving the date of installation. (4-26-2013).  Also present was the furnace installation manual for this Goodman GMH 80 furnace which stated that if a masonry chimney is used as a vent, the chimney must have a metal liner.  No metal liner was present.   

Online city permit records show the permit was issued April 30, 2013, for a furnace & AC. The city final inspection was on 5/17/2013, and approved by inspector Todd T.

The furnace is an 80% AFUE induced draft model. (Fan-assisted category 1)

An article entitled Venting Gas Appliances by Bob Dwyer & Mark Gronley in the Feb. 2003 Journal of Light Construction, outlines the reasons why the furnace needs to be vented into a metal liner.

“Fan-assisted Category I furnaces use an inducer fan to overcome air resistance in the combustion chamber but do not pressurize the vent system. No dilution air is introduced, so the exhaust is damp and condenses readily.”

A few basic do’s and don’ts will take you a long way toward getting good results:

• Never use unlined chimneys. Avoid masonry chimneys even with tile liners.
Reline chimneys with listed liners or B vent.

Chimneys are especially vulnerable: Acidic condensate eats through tile flue liners and destroys brick masonry.” END OF QUOTE.

Our inspection report had a photo of the interior of the chimney showing the lack of a metal liner, a correct listing of the age of the furnace, a statement indicating the installation was not in conformance with the furnace manufacturer’s requirements and increases the potential for moisture damage to the chimney. We recommended the installation of a liner or furnace replacement with a high efficiency sealed combustion model that does not use the chimney. While not in our report, the cost estimate for the replacement furnace would be about $3,000. Also see Attic Inspections are necessary.

The City of Minnetonka response is: “We are very proud of the quality and consistency of the inspections conducted by our city inspectors at both homes and businesses in Minnetonka,” said Bob Manor, city of Minnetonka building official. “However, we are providing an inspection at a certain point in time, often when work has already been completed. In this case, we missed a manufacturers requirement we should have caught. Once it was brought to our attention, we offered to re-inspect the work, but the property owner didn’t take us up on that offer.”

“Our city inspectors are highly trained professionals who have caught many more potentially dangerous or hazardous conditions than they have missed, so I continue to believe in the value of our inspections to protecting the health and safety of our residents,” Manor finished.  End of Minnetonka response.

We found several less costly concerns including:
(C) 2014  Disturbed / displaced attic insulation,.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO                 Displaced and compressed attic insulation (visible in ERC photos)
                 (C) 2014  Electric panel with 4 uncapped openings.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO
          Uncapped openings in the front cover of the electric service panel
         (C) 2014  Electric wiring for former hot tub exposed on patio.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO
      Exposed wiring on the rear patio for a former  hot tub (visible in  ERC photos)
(C) 2014  Sump pump discharge with inches of a window well.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO
        Sump pump discharge was within 2 ft of the house foundation

(C) 2014  Signs of leaks near water meter.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO (C) 2014  Prior leak at valve above  water meter.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO


Water intrusion questions raised in the ERC report were found to be a prior slow leak at the main water valve.

We also found that the ERC report included a completely false and distracting comment about the lack of a fireplace damper clamp for a “gas fireplace log”.  No gas fireplace log was present, and NO evidence was found that there had EVER been a gas line installed to ANY of the fireplaces in the home.  

Our customer was very pleased he chose to have an inspection done on his behalf, since the final resolution of this matter was that the heating contractor replaced the furnace with a direct vent sealed combustion furnace that did not rely on the chimney for venting.  

                       A rare, but potentially serious furnace maintenance error

An early June 2016 home inspection included finding a gas forced air furnace with its covers reversed.  The air tight blower cover was on the burner compartment, and the louvered burner compartment cover was on the blower cabinet. The 24 year old furnace was a Carrier model 58WAV. Carrier made this model from about 1992 until at least 2000.  I do not recall seeing another furnace with reversed covers prior to this inspection
 (C) 2016  Furnace with reversed upper & lower covers.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO   

The result of the misplaced covers was an extremely dirty system since the blower cabinet was pulling in unfiltered air.  Our report recommended the system be cleaned and corrected by a qualified HVAC firm. We further stated that the furnace was at the end of its normal service life.


Nine days later, I found another Carrier 58WAV furnace, 21 years old, with the same reversed covers situation.  In this case, the furnace was clean enough to operate briefly. However, a carbon monoxide test in the vent produced results consistent with a heat exchanger defect. (CO levels rising after the blower came on.) 

  (C) 2016  Furnace with reversed upper & lower covers.  Photo by Roger Hankey, ASHI Ceritified Inspector Winter Park, CO          Two Furnace models with identical upper & lower covers. Drawing by Carrier  

This furnace is VERY similar to its down-flow twin, model 58ZAV. The image shown at right compares both models. Notice the similar size, shape, and cover designs. 

These images suggest that Carrier found it cost effective to make the covers fit either furnace.  There is no marking on either cover to inform the owner or occupant of the proper cover locations.  Both covers will fit in either location and when installed, both will depress the blower safety switch.  This model furnace was also offered in the Bryant label and other brands built by Carrier.


Persons unfamiliar with furnaces or who have only seen down-flow furnaces may not realize the proper cover position on up-flow furnaces, and vice versa.  While it is easy to correct reversed covers, the consequences of reversed covers include poor air circulation particularly in cooling mode, improper combustion due to insufficient air in the burner compartment, and if the covers have been reversed for an extended time, inefficient heat transfer due to dust coating all the surfaces of the heat exchanger and cooling coil. Additionally, if an atmospherically vented water heater is alongside the furnace, the unrestricted airflow into the blower has the potential to downdraft the water heater.   


While researching this story, I was able to find only one other inspector’s website with an image or discussion of reversed furnace covers. His example was a Trane furnace.


HOME INSPECTORS: When encountering any of these very popular furnace models, it is recommended you explain the proper cover location to the customer and mark the proper locations on the covers, in addition to recommend cleaning and any other necessary corrections by a qualified heating & cooling contractor. 


Great information on Furnace filters from Carbon Monoxide Myths (see their website for more good information)

Good filters, dirty filters, no filters … have no affect on whether your furnace will produce carbon monoxide.  However, they can have a profound effect on your overall well being and equipment life.

Effects of Dirty Air Filters

During Winter:

·        Causes reduced air flow. 

·        Causes furnace to discharge higher than normal air temperature. 

·        Cause an abnormal temperature rise across the heat exchanger. 

·        Could cause stress cracks in the heat exchanger, singed wiring and a number of other issues. 

·        Decrease system efficiency by increasing the heat-loss of the duct work. 

·        Allows dirt accumulation on air-conditioning coil. 

During Summer:

·        Causes reduced air flow.

·        Can cause air-conditioning coil to form ice or freeze up completely.

·        Can lead to “liquid slugging” at the compressor.

·        Can lead to un-even cooling between rooms.

·        Can cause ducts to sweat.

·        Greatly decreases system efficiency.

·        Increases operating costs.

·        Allows dirt accumulation on air-conditioning coil.

Once dirt accumulates on the air-conditioning coil, system capacity is reduced and eventually the air-conditioner stops working.

So – don’t  forget — change your air filters at least every three (3) months. Change them every month for optimum efficiency.



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