Posts Tagged ‘air conditioning systems’

What goes out must come in

December 5, 2010

On my Linked In page, I passed on a link to an article titled, “Makeup Air for Range Hoods” (  The author, Martin Holladay, digs into the details of adding a larger range hood to a home.  In particular, he investigated whether consumers were warned about what could be the impact of adding such a hood to a home.  Mr. Holladay’s blog is a fair warning to consumers that they might not be warned about products that could have a negative impact on your home’s environment, and that impact could be hazardous.

In this post, as I promised on my LI page, I am going to dig into more detail about the impact the fan or other devices that change home pressurization could have on the home and potentially its occupants.  Let me start the same way.  Consider your home–or any building for that matter–as a box.  When air is removed from that box, replacement air has to come into the box to replace the air that is removed.  This replacement air is normally called makeup air by building professionals.  The issue is from where that makeup air comes.

If the home is air leaky, makeup air will come through openings in the building’s exterior shell, i.e. walls, roof, windows, doors, etc.  Leaks are usually a major issue because the air can come from many places.  Rehabbing older homes cuts down on the leaks, but usually cannot totally eliminate them.  But, even newer, so-called tight, buildings have air leaks.  The problem with air leaks in all buildings is mainly a thermal comfort issue because leaks cause drafts, and few people enjoy the feeling of a cold air stream inside the home on a cold day.  Another just as important issue is that if air can come in through a leak, it can go out through a leak, which translates into loss of heated or cooled air.  But, air streams flowing past hoods, fireplaces, ventless heaters, etc. can impact their operation.

Air is a lot like most people in that it takes the path of least resistance.  So, air coming through leaks can mess with the home’s return air system.  For a heating and air conditioning system to work properly, adequate air of a certain temperature has to be supplied to an area to compensate for the heat gain or loss from that area.  What may no be known is that air has to also be removed from the area to help the supply air side of the system work right.  In buildings with poor return air systems, large temperature differences could exist from one area to another even if the supply air flow is ideally designed and installed.  What can happen is that air entering through leaks has the path of least resistance to the air handler.  That air, then, prevents the return air system from returning air back to the air handler from some (or all) of the building’s areas.  Those areas that do not have proper air return will be hotter or colder, depending on whether the air handling system is in the cooling or heating mode, respectively.  Alternatively, those areas through which the leak air is traveling could be too hot or too cold.

What about buildings that are pretty well sealed?  If the exhaust fans in the home do not have adequate makeup air, they will either not move as much air as designed or makeup air will come from wherever it can, which might be from undesirable places, such as through flues or chimneys.  The condition of air flowing in the reverse direction from which it is intended is called backdrafting.  When backdrafting occurs in flues and chimneys, combustion gases, including carbon monoxide, could be pulled into the home.  When wood is not being burnt in the fireplace, backdrafting air can pull creosote emissions into the home, which believe me is not a desirable fragrance. Backdrafting can also impact combustion of some appliances, making them less efficient.

What if a combustion appliance, such as a water heater or furnace, have flue booster fans that are supposed to push the exhaust gases outdoors.  If the appliance is a closed system, such as many of the higher efficiency furnaces, no impact should be expected because closed systems pull air directly from outdoors.  Appliances that pull air from the general building air, as do the water heaters with flue fans, may be affected, depending on which fan in the building moves more air or other characteristics.

The impact that exhaust fans could have on other combustion appliances is not unknown to building professionals, though.  Some homes with furnaces that used general home air for combustion have a duct that runs from outdoors to somewhere in the vicinity of the furnace.  That is all.  This duct is not connected to any fans or any other devices.  This duct is simply a path for air to travel from outdoors to indoors to makeup air removed from the home.  Do they work?  Maybe.  But, as I said earlier, air takes the path of least resistance and, if the duct is not the path of least resistance, it will not work.

The concern as stated in the blog post cited at the beginning of this blog in particular was discussing the installation of large kitchen exhaust fans that move over 1000 cubic feet per minute (cfm) of air.  That is an extraordinarily large fan for a home.  Will the usual kitchen exhaust fan cause the same issues?  If it doesn’t exhaust air outdoors, which is normal for these fans, the answer is most likely no.  If the fan exhausts air outdoors, the answer is maybe.  By itself, the fan likely will not cause backdrafting at the least.  That fan in combination with other fans might cause backdrafting.  Again, if the home is air leaky, any exhaust fan can pull air through leaks, causing thermal comfort and/or heating or cooling efficiency issues.

Are exhaust fans the only things that can cause air leakage or backdrafting issues?  Well, no.  All buildings have a chimney effect where heated air rises within the building.  As this air rises, air is pulled into the building at lower levels.  The chimney effect is for the usual home is definitely not as great as that for a high rise building.  In most homes, backdrafting due to the chimney effect is likely not an issue; but the chimney effect can cause drafts in lower parts of the home.  The only way to know whether a backdrafting or draft issue exists is through investigation.  A homeowner might be able to investigate the issue using smoke from an incense stick or other air flow indicator.   However, a professional will know more about the conditions to which to test under and will have more sophisticated instruments than a homeowner.

So, if you have this favorite nook in your home that sometimes feels comfortable and then other times feels drafty, consider that the reason could be an exhaust fan or the home’s air handler pulling air through a leak.  What to do about it from there is up to you.

A potential Freon fiasco

March 8, 2010

One of the inspector message boards recently posted a letter from one of the home warranty companies to realtors about Freon.  The parts of the letter related to most homeowners are duplicated below:

Starting January 1, 2010, a new Environmental Protection Agency (EPA) mandate will change the way your clients’ home

air conditioners are serviced and repaired. At that time, manufacturing HVAC equipment that primarily utilizes Freon®

(also known as R-22 and HCFC-22) will be banned, and the nation will begin using products such as Puron® (also known

as R-410A) as the standard refrigerant for air conditioners. This change will affect your buyers and sellers in many ways.

Costs will increase

A variety of factors will lead to increased costs:

  • R-22 parts may no longer be available.
  • Since R-410A parts are not always interchangeable with R-22 parts, replacement of the entire system might be necessary.
  • Physical changes to your system may be needed to accommodate the larger equipment required in air conditioners using R-410A refrigerant.
  • The supply of R-22 refrigerant will be limited, causing the price to increase.
  • Repairs may take longer because you may want to explore your options and wait for less expensive parts, if they are available.
  • New HVAC equipment may be more expensive to purchase and install.

Manufacturers’ warranties may not provide full coverage

Typical manufacturers’ warranties only cover parts for one year, in most cases. Labor is a significant part of any repair.

Each manufacturer may take a different position if an R-22 system cannot be repaired or parts are not available.

System and appliance warranties/ service contracts typically exclude coverage resulting from government mandated changes

Most system and appliance home service contracts/warranties contain language that effectively excludes the additional

costs resulting from this government-mandated change. Each home service contract may deal with this situation


Visit to answer all your questions concerning the impact of this new government mandate to you and your clients or call 877-777-3188 to deliver real time answers to agents and homeowners.
Even though the letter was originally written to realtors, it contains information that is important to homeowners, particularly the parts about prices of the Freon alternative.  But, one other part of the letter, which I did not include here, was that homeowners who are selling will likely now have to disclose any Freon systems.  As home buyers get wise to the Freon system problems, sellers will likely end up reducing their selling price because of the Freon problems.  Likewise, if you are in the market for a home, you may want to ask about whether the air conditioning system uses Freon.  Most likely it does or it will (depending on which side of the sell you are on).  That means in turn that older air conditioning systems that need repair might end up being cheaper to replace than repair.

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