Practical thinking for the ACH number…..
Last week I mentioned the importance of paying attention to your ACH (Air Exchanges per Hour). We focus on air sealing and good design for better insulation based on Building Science to keep the ACH number below 3. What this means is that your home will hold temperature better thus your heating and cooling system won’t have to work as hard.
The State of Washington building codes require a 90% efficiency or better heating system. Most builders use this as their energy efficient home thought process. They put that furnace in and that’s it. They have an energy efficient home—or do they?
Let’s think about this for a minute. A 90% efficient furnace has a 10% inefficiency. Every time you have a heat exchange (an ACH) you lose 10%. Every time.
If an average home has 15 ACH’s per hour then you will have 1.5 ACH’s lost as inefficiency. Consider that there are 24 hours in a day at a loss of 1.5 ACH’s per hour is a total of 36 air exchanges lost—vroom gone— Every day.
We keep our ACH’s at about 2.5 per hour which equates to a .25 loss of an ACH per hour or 6 air exchanges lost in a 24 hour period.
Think about this—36 ACH’s lost versus 6 per day. How about 13,140 lost per year versus 2,190. Which would you want?
Keep in mind—the same furnace is used— You get the idea. IT’s DRAMATIC. IT’S REAL.
Our thought process has changed dramatically. Having a 90% or more efficient furnace is good. But, how good is it if your home is not sealed and insulated properly. Wouldn’t it make more sense to focus building codes towards sealing and insulating better? We think so. That is why we do it.
You should to. If you have an existing home go get that energy audit. You will be amazed.
Build well and enjoy life.
Please submit questions to firstname.lastname@example.org Jon can be reached direct at 360.907.5800. Tune into Green Building with Jon Girod on 1550 a.m. on Saturdays at 9 am. See you next week!