Home Ventilation and Pressure - It is becoming increasingly necessary to have your home checked for home pressurization. Does your home have a negative pressure inside of it? Do you have a gas or oil furnace which is inside the home and uses the air in the home for combustion air to fire the furnace or boiler? Do you have other gas or oil burning appliances, a fireplace, gas logs, or anything which consumes air inside the home? This does not refer to furnaces which are located in the attic (unless you have a completely sealed attic or the attic has a maximum height of less than 30 inches.)

These appliances consume air and along with some other air consuming appliances in your home the issue of home pressure and home ventilation come into question especially in this day and age when the drive is on to increase efficiency and reduce energy consumption. Homes are being built tighter with better insulation, doors, and windows. Less infiltration air is being fed into the modern homes of today so it’s important to give the home a safety check to make sure there is enough air left over for the occupants of the home.

Home Ventilation and Pressure - The Design, Construction, and Code Considerations

Home Ventilation and PressureMany architects and engineers who design homes know that all systems and structures must comply with building codes and all of this is considered in the design process of any structure. The plans for major developments and homes are also reviewed and approved by local building code officials long before construction takes places. All trades involved in the construction of these buildings or homes also are familiar with codes so there are many safety factors and layers to the construction of new buildings before they are built, while they are being built, and after they are built when all the final inspections occur.

There should be nothing to worry about but what about existing housing or buildings where the owner undertakes improvements without obtaining permits or having licensed professionals who are familiar with safety factors and building codes do the work. One small change here and another small change there and then a major improvement like new doors and windows and suddenly a problem may exist that no one is aware of. Suddenly more air in the structure is being consumed by different appliances than is allowed inside the structure through natural ventilation and infiltration air. How can this occur?

Home Ventilation and Pressure - Do You Know the History of Improvements?

New energy efficient doors and windows mean no more leaky drafts which at one time the leaky drafty windows and doors, while inefficient and adding to the energy costs to keep the building comfortable, provided some infiltration air into the structure but now that is gone. Perhaps someone got a new range hood for the stove in the kitchen. The exhaust fans in the bathrooms were upgraded. More insulation was dumped in the attic and crawl space which further reduced infiltration air into the structure. Someone checked all the receptacles in the house and found they were a source of drafts and used insulation spray foam to block the drafts which can come from the electrical receptacles.

Maybe gas logs were installed or an old fireplace restored and put back into use. Maybe the previous owner of the house also blocked off some of the ventilation in the furnace room or basement because they thought this was a source of drafts and cold or hot weather coming into the building. Any of these things can occur and they reduce the amount of fresh outside air which comes into the building. There is a balance though and if the balance tips in the wrong direction problems or even a dangerous condition may exist.

Home Ventilation and Pressure - Combustion Air and Dilution Air for Furnaces or Boilers

There are furnaces and boilers which are high efficiency which pull all the air necessary for their efficient and safe operation directly from outside of the building. This air is sucked into the furnace through a pipe by a fan where the air is used for combustion and then the combustion gasses are vented outside of the structure to a safe place where no one is harmed. Not every home or building has these types of furnaces or boilers. Some furnaces and boilers need to be fed air from within the structure itself and when these necessary appliances were installed an inspection took place which approved of this appliance, its safe operation, and the fact that it consumed air from inside the structure for combustion purposes.

What has changed with the structure in the last few years or even the last five years or however long this appliance has been in operation? Was the fact noted that this appliance needs air for combustion purposes or was this overlooked? Without the proper amount of combustion air the furnace or boiler will produce more carbon monoxide and depending on the pressure this carbon monoxide can be introduced into the home given the right circumstances that include home pressure.

Home Ventilation and Pressure - The Mechanical Code and Combustion and Dilution Air

Chapter 7 of the International Mechanical Code covers combustion and dilution air required by many boilers and furnaces. It covers air requirements for furnaces and boilers located in closets, attics, crawl spaces, and mechanical rooms to name the most prevalent places these appliances are located. There are other building codes which address the issue of combustion and dilution air for appliances which consume air. This was looked at when the new furnace or boiler was installed and it is a major consideration in all mechanical inspections of furnaces and boilers. Again, we know that this was looked at when the furnace or boiler was installed.

We know that the mechanical inspection took this into consideration when the final inspection of the boiler or furnace was installed and put into service. We may even know what has changed with the home since this installation and final inspection took place but do we know if those changes, whether small or big, took the combustion and dilution air into consideration?

Home Ventilation and Pressure Test

Home pressurization and home ventilation are very important for the occupants of the structure. Good fresh air in the building is better and healthier than old stale air which has been trapped in a space for a prolonged period of time. A good home pressure and ventilation test will tell you if you have enough infiltration air coming into the home to feed every appliance in the home including the furnace or boiler. Requirements for this include a test instrument called a manometer and it is very important that this instrument be properly calibrated for the test results to be accurate. The manometer reads extremely low pressures measured in inches of water column.

Your local HVAC contractor should have this instrument as it is commonly used in many different HVAC applications. First, all the doors and windows in the building should be closed tightly just as you would close them on the coldest day of the year. All appliances and exhaust fans are off including air conditioning and heating systems. The manometer is turned on and the pressure noted. It should be a slight positive pressure. Next, the heating system is turned on. The heating system should run for at least ten minutes and the pressure on the manometer noted again. The pressure should not have changed too much. Next, with the heating system on turned on all other air consuming appliances which include gas logs, Jen Air cooking appliances, range hoods, and exhaust fans in the bathrooms and any other places where they are installed.

If the gas logs are ventless gas logs it is a good idea to test the CO2 levels in the home at this time also. Everything should run for another ten minutes and if the manometer has a negative reading then you have a problem with the proper amount of air coming into the home. Ventilation needs to be added to ensure the home never starves for fresh infiltration air. It is not out of the realm of possibilities that the heating system be running and other things which consume air are running in the home also especially with all the doors and windows closed. Proper home ventilation will prevent this scenario from occurring in the home.

Start with ensuring the furnace or boiler have the proper amount of combustion air available to safely heat the home and you can sleep much better at night knowing that the proper amount of air is being vented into the home for your health and for your appliances. And know can deny that a good nights rest is good for our health. Have this home pressurization and ventilation test performed on your home so you can get this good nights rest.

Other resources concerning home ventilation can be found here.

High Performance HVACHome Ventilation and Pressure

 

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