Can My Home Be Sealed Too Tightly?
There is a catchy phrase right now that is growing in popularity among top builders: “Build it tight and vent it right!” We really need to change the conventional wisdom of ventilating houses. Vented crawlspaces are a very bad thing. Most good builders have switched to sealed, insulated, conditioned crawls…but that is just the beginning.
When it comes to home construction, there really is no such thing as too tight. We want our homes to be airtight, then we bring in the right amount of fresh air through intentional ventilation rather than unintentional infiltration (air coming in through uncontrolled places like leaks in the crawlspace). We also want to control exhaust ventilation such as bath fans, range vents, and other exhaust when needed (i.e., radon control fans). The incoming fresh air and the outgoing exhaust air should be balanced.
The Whole Home Approach
I often preach about the domino effect in home construction and tightening our homes is one of the biggest problems. To be clear, tightening our homes is a very good thing, but it can’t be done with tunnel vision. You must look at a home holistically and address everything together. In the world of physics, air is considered a fluid just like water. If you think of your house as a boat and the outside air as water, wouldn’t you want to be pretty certain there are no leaks? Once we accept that we need the tightest house possible, we now need to look at what is going on inside the home.
Let’s think of a super tight house as a glass jar– everything going on inside it will remain unless it is intentionally removed. Indoor air quality and humidity are the two biggest safety and comfort areas to address. Cooking, cleaning, new products like carpet paint, and even people all can combine to create hazardous air quality. Cooking with gas, for example, can create carbon monoxide. Lots of other foods (like microwave popcorn) put off gasses (“offgas”) we do not want to breathe. The chemicals we clean with can be very toxic as well: bleach and ammonia are in a lot of cleaners and even drier softener sheets can contain benzene, which is a known carcinogen. Paint, new carpet, and products like vinyl shower curtains can offgas volatile organic compounds (VOCs) for many years.
Balancing Your Home’s Indoor Air
All of these combine to make indoor air quality a very important thing for us to control. Balanced fresh air ventilation is actually very easy to achieve with simple products like Energy Recovery Ventilators, it just takes a good plan and a educated contractor like Synergy Home!
Correcting Moisture & Humidity Issues
Humidity or moisture in general is the next thing we need to focus on. Over the last 7 years, I have seen numerous cases of mold and mildew on newly constructed homes. In every case, these problems have arisen because the HVAC contractor did not properly account for the air tightness and insulation values.
It seems that 3 years is the magic number for the mold and mildew to start forming. Anecdotally, I believe this is because the home’s interior can absorb a certain amount of moisture. As the seasons come and go over a couple of years, the interior air begins to get saturated. This is an especially big issue in the high humidity seasons of spring and fall, since many times we aren’t running heat or air conditioning to control the moisture. Going back to the 3 year timeline, it takes about 3 years for our vents to build up enough dust and dirt for the condensation to become an issue. This is a perfect recipe for mold and mildew to develop. In addition to this, the average human releases 2.5 GALLONS of moisture into the air on a daily basis through respiration, perspiration, bathing, and cooking. This means a family of 4 is putting 10 gallons of moisture into their home every day!
So now that we know what the problem is, how do we avoid it?
Mold Remediation & Solutions with Synergy
There are several solutions to mold problems, most of which have to be addressed by the HVAC contractor like Synergy Home. Many heating and cooling contractors never fully embrace the “V” in HVAC. “V” stands for ventilation and it is represented by my “vent it right” expression!
We need to address ventilation in a balanced way because in a tight house there is not enough leakage to supply exhaust fans with enough air to exhaust. Bath fans, range vents, and even your clothes dryer have traditionally relied on leakage in the home to supply them with air to exhaust.
Remember the glass jar analogy: if there are no leaks in the jar, you will not be able to exhaust any air. Starting in 2015, all kitchen range vents over 400 cubic feet of air per minute had to supply their own fresh air by building code. You must work with an HVAC contractor that understands proper ventilation and the strategies to keep your home’s air balanced.
Learning to Live in Your New Airtight Home
Another major solution to these issues is educating the homeowners. We always show our customers how to live in their new airtight home. Many of the problem homes I have visited had similar issues, the most common being people just don’t run exhaust fans. Whether the fan is too loud or they simply just forget, it won’t do its job if you don’t turn it on! Some of this can be avoided if it is addressed during the design stage. I regularly recommend humidity-sensing exhaust fans to my customers that will automatically come on when the humidity gets too high. I also recommend installing super quiet fans so that the sound is not an annoyance. A good contractor will design a system like this that will take away these excuses before they happen.
With many of us experiencing more and more allergy issues, proper design of the home’s heating, cooling, and ventilation is critical for a comfortable healthy home. Though we’ve mainly addressed these topics as they pertain to new construction, the issues are equally (if not more important) for tightening an existing home.