Essentially...if I did my math correctly...my house is fairly tight and is just above Energy Star 2.0 standards (ACH50 = 5.1; Energy Star 2.0 <5.0). You certainly can't complain about this given that New Homes barely meet this standard with existing homes (like myself) are generally have ACH50's in the 10-20 range. BTW...ACH50 is "Air Changes per Hour at 50 pascal". That's the blower door test standard which simulates the pressure differential with a 20 mph wind. I found this table online (I've yet to re-find it...if I do, I'll post the reference) which is a good description.
| ACH50 | Natural Air Change | Rating | % of Energy bill | % savings potential | Ventilation requirements |
| 1.5 | 0.075 | Super | 2% | none | Requires constant energy recovery ventilation |
| 3.5 | 0.18 | Excellent | 6% | 1 to 3% | Will require occasional forced ventilation |
| 5 | 0.25 | Better | 10% | 2 to 4% | May require occasional forced ventilation |
| 7 | 0.35 | Good | 14% | 2 to 5% | Does not require additional ventilation |
| 10 | 0.50 | Fair | 20% | 3 to 10% | Start of excessive energy loss and over -ventilation |
| 20 | 1.0 | Bad | 40% | 5 to 20% | Excessive energy loss and over –ventilation. |
The duct blaster showed my upstairs ductwork was better than energy star (3.69 CFM vs Energy Star <4 CFM) with the downstairs ductwork at 7.8 CFM****.
**** We found after the test that the door to the filter at the downstairs airhandler was had some big gaps/leaks. I have HVAC-taped over the gaps when I reinstalled the filter. It's expected that these leaks were the cause of the unexpectedly high leakage...and now the downstairs ductwork should meet Energy Star standards. ****
We'll see what the final results say...but I'm guessing it's going to say that my house is doing pretty well.
One thing I was hoping for, was that going through this exercise would identify my next project. Well...it kind of didn't.
When we walked through the house with the IR camera (blower door maintaining -50 pa), we really didn't spot any significant air leaks. That's good, right? There were some very small spots, but nothing to raise an eyebrow at. And those small spots I can most likely fix with a small tube of caulking.
So where does this leave me?
Most likely I'm still doing the following projects:
1) Geothermal hot water heater. This is adding in the second tank to optimize hot water generation
2) Insulate crawl space walls (R10) and make the crawl space part of the building envelope. This should keep my downstairs wood floors warmer during the winter.
3) Siding and housewrap. I still want to replace my siding with Hardiplank really for looks. But while I'm at it, I'm probably going to add in an air barrier. Given my results...a simple housewrap will probably be sufficient (per my previous posts I was looking at adding in some rigid insulation). From the Table above...I really don't have much % savings potential left. So the simple housewrap should put me firmly in the ACH50 <5 catagory, if not approaching a ACH50 of 3.5.
I should get the results of the audit next week...and of course, I'll fill y'all in on the details...
Happy Memorial Day1
