This post is written as a conversation between a homeowner and myself as it could have occurred during a Home Energy Audit. It is actually the gathering together of several conversations on different audits over the past few years.
A Healthy Home is Free of Combustion By-Products
Homeowner: Oh! You mean no Carbon Monoxide! I have a Carbon Monoxide Detector. It has had some false alarms, but it has never found a problem.
The Energy Guy: OK! Carbon Monoxide (CO) is one by product of combustion. There are others.
Homeowner: So, you mean the house must be all electric?
The Energy Guy: No, not necessarily. An all electric home, might have a fire place, and an attached garage. Both are sources of CO and other byproducts of combustion. A healthy home will deal with all of these in some fashion.
Homeowner: What other things are you talking about besides CO?
The Energy Guy: The one I see the most of is moisture. Many of the flue pipes I’ve seen have rusted from the moisture. If you have a gas hot water heater, look at the top. Is the top rusting, what about the flue pipe or the draft diverter? Moisture from open combustion appliances also increases the humidity in the home and adds unneeded work to your air conditioning unit, increasing the bill.
There are others, such as Nitrogen Dioxide, and Sulphur Dioxide, and various particles of all sorts.
Homeowner: So, those are like Carbon Dioxide? Something that is just there?
The Energy Guy: Yes! They are just there, with two concerns. First the Lung Association points out the health effects of Sulphur Dioxide include:
- Wheezing, shortness of breath and chest tightness and other problems, especially during exercise or physical activity.
- Continued exposure at high levels increases respiratory symptoms and reduces the ability of the lungs to function.
- Short exposures to peak levels of SO2 in the air can make it difficult for people with asthma to breathe when they are active outdoors.
Health effects of Nitrogen dioxide include:
- Increased inflammation of the airways
- Worsened cough and wheezing
- Reduced lung function
- Increased asthma attacks
- Greater likelihood of emergency department and hospital admissions
- Increased susceptibility to respiratory infection, such as influenza
Homeowner: I’m pretty healthy, but you said ‘First!’
The Energy Guy: The second is moisture. Moisture could be a high humidity situation, or moisture from the combustion that produced these dioxides and if you inhale some of them, or moisture in your nose and lungs. Here are the basic chemical equations for those interested.
Sulphur Dioxide plus Water ends up as Sulphuric Acid [SO2 + H20 ===> H2SO3 (sulphurous acid) SO3 + H20 ===> H2SO4 (sulphuric acid)]
Nitrogen Dioxide plus Water ends up as Nitric Acid [NO2 + H2O ===> HNO3 + NO]
Homeowner: But acid eats things up!
The Energy Guy: Yes, it does. These acids start the rust process, I mentioned earlier. The other place you can look for rust is to look at the flue on the roof of some homes. If the coating is attacked by the acids, then rust occurs.
So How do I keep this stuff out of my home and away from my family?
The Energy Guy: First install some Carbon Monoxide Detectors. If your furnace and water heater are in the basement, you need one down there. You also need one near bedrooms.
Homeowner: OK! I’ll get that one that works with my Nest!
The Energy Guy: That will work for one. The Nest Protect is like most CO detectors, it will alarm at the higher amounts of CO as required by the Underwriters Laboratory requirements. These start at 70ppm of CO for an hour. Professional organizations such as ASHRAE and NIOSH list 35ppm as the level for technicians and others to stop work, turn off equipment and evacuate the building. A low level detector is important.
Low Level CO detectors do not meet the UL requirement because they alarm at lower levels, typically 20ppm. 15-20ppm CO levels have been found to impair judgement in people exposed for short periods of time. The UL testing does not allow a CO detector to pass if it alarms below 30 ppm. Low level CO exposure can result in headaches and general malaise. If you are exposed to low levels over a period of months or years the effect is unknown at this time.
Homeowner: OK! So I’ll get a low level detector also. What else can I do.
The Energy Guy: Do some careful air sealing between the garage and the house. You can add exhaust ventilation to your garage as recommended in the International Residential Code. Open the door before you start the car, and then immediately back out. More information about CO and the garage. Air sealing here and a simple closer on the door to the garage will help keep CO and other pollutants from the garage out of the house.
Inside the house, you can buy smart when you replace your water heater or furnace. Buy sealed combustion units. These are generally more efficient units, so they will save you some on your bill each month.
Water Heaters can be sealed combustion, such as the demand models or a power vented unit. Either of these units can be identified with the use of PVC exhaust flue, instead of the metal flue needed by traditional units. They do not need the metal, because the exhaust is a lower temperature. This has a side effect of increased efficiency. The image to the right is the flue of at sealed combustion furnace.
Finally, think about your wood burning fireplace or your gas oven. These also create the same problems. Here a low level CO detector would be very valuable. Following the fireplace manufacturers instructions in keeping the glass door shut and having it checked regularly are important. For a gas range, especially with a gas oven, install an exhaust fan that vents to the outside.
Some of this information came from the Maine Indoor Air Quality Council
Some of this information came from the American Lung Association
A Healthy Home — The first of this series