Most of us don’t think too much about air quality inside the home. But Portland summers come with a good amount of outdoor air pollution from wildfire smoke, increased traffic and heat-related ozone, all of which can infiltrate the home. The good news is that one of the most important actions you can take to improve indoor air quality — air sealing — can help improve your Home Energy Score, too. And if you’re telling yourself “my HVAC system filters the air in my home,” it’s not completely untrue — but skip to the last section of this post to learn about some common ways that the HVAC system fails.
Indoor Air Pollution Defined
Exposure to indoor air pollution can have both short-term and long-term health effects, according to the EPA. Here are some of the main sources of pollutants causing poor Indoor Air Quality, or IAQ:
- Wood stoves and other fuel-burning heat sources
- Cigarette or other smoke
- Building materials and furnishings as diverse as:
- Asbestos-containing insulation that has deteriorated
- New flooring, upholstery and carpets
- Pressboard cabinets or furniture
- Chemicals used in or around the home, such as cleaning products, adhesives or herbicides/pesticides
- Central heating and cooling systems (HVAC) as well as humidifiers
Is that all? Well, no — outdoor air pollution becomes indoor pollution when a poorly sealed home allows air infiltration from the outside. In this blog post, we’ll focus on air sealing and HVAC systems, because these factors can impact your Home Energy Score as well as your health!
Air Sealing vs “Letting the House Breathe
It’s a common building science myth that Home Energy Score assessors hear all the time: “Houses need to breathe.” The theory is that air sealing a house too much will prevent fresh air from getting in.
How much truth is in that statement? Not a whole lot. New homes that are built to be airtight are required to have a built-in mechanical ventilation system, which takes in outdoor air from an ideal location and brings it to room temperature before expelling it into the house. These air exchangers are required in Portland new construction and just about everywhere else, too.
Most Portland homes are older (pre-1970), and it’s pretty much impossible to make an older home airtight. There’s always going to be some fresh outside air coming in. Typically, this is a good thing, but when “outside” air is actually coming in through the basement, crawlspace or attic, it’s not as clean as it could be. These locations in the home are notorious sources of dust, mold spore and other contaminants!
To maintain good IAQ, the following steps are very important:
- Seal off the attic and crawlspace or basement. Seal around the attic hatch and can lights, as well as along baseboards and knee walls.
- Block sources of outside air: Check and seal window and door frames, around vents and other openings. Check out our full post on air sealing your home here.
By properly air sealing your home, you have a choice over how much outside air comes in. When outdoor air quality is low, you can keep clean air indoors, opening doors and windows to let the house breathe when it is safe to do so. In addition, you’ll spend less money heating and cooling your home and your home will perform better on the Home Energy Score Assessment.
Still concerned that you have over-sealed your home? An energy auditor can perform tests on your home to check for proper air infiltration, such as a blower door test. Read more about energy auditors vs Home Energy Score assessors here on our blog.
Is your HVAC causing indoor air pollution?
A central heating and cooling (HVAC) system can impact IAQ in a number of ways. Even though HVACs are equipped with filters, they don’t always do the job of cleaning the air, building science consultant Allison Bailes writes in the Energy Vanguard blog. Lack of maintenance, leaky ducts and breaks or gaps in the ductwork are common problems. So even if the air filter is new, IAQ could be compromised elsewhere in the HVAC system.
Before we get into the relationship between HVAC, IAQ and the Home Energy Score, here’s a quick review of how HVAC systems work. The HVAC distributes heated or cooled air from an “air handling” unit, which is typically in the basement or garage. Ducts distribute the air through the entire home — the average home has 30-90 feet of ductwork, most of which is tucked inside walls, in the basement, or up in the attic. Return air vents located on every floor of the home send the air back to the air handling unit via return ducts.
Although the Home Energy Score assessment doesn’t get into detail about the workings of the HVAC system, points are awarded for having a new, efficient system. Of course, even a new system needs to be maintained. It’s a good idea to have an HVAC maintenance professional visit your home once a year and check of the entire system operation, including ducts, blowers, fuel inlet, and drains. They will also calibrate temperature sensors, check electrical connections, and remove dirt and debris from inside the air handling unit. Finally, they’ll replace the air filter, which is an important step toward maintaining good IAQ as well as efficient operation of the HVAC system.
Next, consider sealing and insulating your HVAC ducts to eliminate leakage, improve your Home Energy Score, and get better indoor air quality. Yes, even though ducts distribute filtered air through the home, they can negatively impact air quality if they leak into the wrong spaces. Specifically, the basement and attic. When too much air leaks out into these spaces, they will be at a higher pressure than the house, like blowing up a balloon. This high-pressure air will make its way into the house, which is at a lower pressure because air is being sucked out by the HVAC’s return ducts.
If you aren’t ready to do a full duct sealing and insulating project, at least check the ducts that you can access to be sure that they are connected. It’s not unheard of to find a disconnected duct blowing heated air uselessly into the attic, or a return air duct sucking up moldy air in a crawlspace. Check the filter in the air handler, while you’re at it — a dirty filter will slow down air flow and make the system work harder to keep you warm or cool, wasting energy.
Looking for more energy efficiency tips? Why not order a Home Energy Score today? It’s easy to schedule online, and your lungs will thank you!