fotolia.com / Antonioguillem
Thanks to advances in engineering, materials and construction, today’s homes are tighter than ever before. That’s great news in our effort to reduce energy consumption and save money, but when it comes to the quality of your home’s air, the new levels of tightness that can be achieved can cause some issues.
Proper ventilation is essential for healthy indoor air quality. Common contaminants, such as pollen, or even toxic ones like carbon monoxide can build up inside a structure that doesn’t breathe, creating a hazardous environment for you, your family — even your pets.
The whole idea of a healthy log home is predicated on three things:
1. That you have air exchange; that is, fresh air coming into the house that pushes out and replaces the stale air that’s built up inside;
2. That natural pollutants that can build up, like dust or pollen, or can penetrate a home from the outside are regularly removed; and
3. That any off gassing caused by VOCs (volatile organic compounds), whether from log stains, carpets, adhesives, etc., are managed or expelled.
If your house is built so tight that these three things don’t happen, your indoor air quality could be poor, and the money you’ll save on energy costs could be funneled into unnecessary doctor’s bills.
Of course you’ll want to take advantage of construction technologies (like improved sealants between log courses and taping around windows, doors and ductwork) that will improve the energy performance of your log home. In fact, with the increasingly rigorous energy codes that are out there, you really don’t have a choice. But when it’s all said and done, how do you know how tight your home is, and what you can do about it if it’s too tight?
A simple blower-door test will measure how tight your home is. Once your logs are up and the house is weather tight (meaning the roof, doors and windows are all installed), a blower-door test will show the rate of air exchange in your home. This is reflected in what’s referred to as an ACH (air changes per hour) rate, which measures the air that’s added or removed from a space divided by its volume. An example would be three air changes per hour at 50 pascals of internal pressure, shown as 3ACH50. This reading would indicate a super-tight log home that’s likely in need of mechanical ventilation to keep the indoor-air quality clean and healthy. By contrast, a home that reads 5ACH50 (five exchanges per hour) is still “tight” but breathes on its own a little easier, meaning natural ventilation, like an open window or two, may be enough to keep the air quality high.
With or without an open window, Mother Nature has two ways to ventilate your home: wind and what’s called “the stack effect.”
When wind blows on the exterior of a home, the pressure will cause some of that air to enter, especially around windows, doors and even electrical outlets located on exterior walls. It will cause the air to move horizontally — in on one side of the house and out the other.
The stack effect happens when warm air rises, causing upward pressure on your home’s interior air. The stale air is pushed upward and escapes through gaps on the upper floors and around the roofline.
So if your interior-air exchange needs a little support beyond what nature provides, what can you do about it? The answer could be as simple as an ERV (energy recovery ventilator) unit. This inexpensive apparatus acts as a respirator, of sorts, that augments your HVAC system. It simultaneously exhausts your stale indoor air, exchanging it for fresh air from the outside, but allowing your HVAC to condition that new air to a seasonally adjusted temperature before it’s forced into your home. And, depending on your climate, a humidifier (for drier regions) or dehumidifier (for humid areas) may be a wise investment to kick your indoor-air quality up another notch.
Getting the best possible experience from your log home is more than how beautiful it looks — it’s about how comfortable it is to live in. Making the most of your indoor-air quality will also help you make the most of the home you love.
Illustration: EnergySEAL Air Barrier Systems LLC
Know Your System
According to SmarterHouse (smarterhouse.org), a project of the American Council for an Energy-Efficient Economy (a nonprofit that acts as a catalyst to advance energy efficiency programs and technologies), approximately two-thirds of U.S. houses use forced-air systems to move heating and cooling energy from a central furnace, air conditioner or heat pump around the house using a duct system. Don’t confuse this air-movement with ventilation — a forced-air system controls how conditioned air is distributed within the house, not how air enters and exits, which is vital for clean indoor air.
Change Your Filters
All this extra effort to clean your air is for naught if your home’s air filters are dirty. Air filters are cheap, easy to replace and essential to the health of your log home. How often should you change them? If it’s a vacation home, every 6 to 12 months will do. For a permanent residence without pets, change them every 3 months; add a dog or a cat, make it every 2 months.
Dan Mitchell is a builder and a Log & Timber Home University professor. He owns Eagle CDI, a construction firm based near Knoxville, Tennessee.