ACH?

jp_2

50 pascals is eqiliant to .2 WC(inches of water). sounds like just a slight pressure difference, enough to tell leakage I'd guess.

Uni R_2

Can someone explain ACH?

I paid for an energy audit a few years ago. They were providing basically a tag like an energy rating on an appliance (except it was for the house). Unfortunately it never included any ACH data and I never knew who to call to get it.

So they called the other day to do a follow-up. While talking to them, they looked up the old data and told me it was 4.5 @ 50 pascals. 4.5 sounds really high but I'm not sure if it is at 50 pascals pressure. Is that moderately leaky or very leaky and at what pressurization levels are these numbers normally given?

Thanks in advance...

Bob Harper

Blower door data

Go to www.infiltec.com and www.energyconservatory.org for info. on blower doors. Get the manual for the Minn. Blower Door ($10).

There are three main numbers they generate:
CFM50 cubic feet per minute leakage at 50 Pascal depressurization.
ACH or air changes per hour
ELA or equivalent leakage area
The minimum infiltration rate for a healthy house is 0.35 ACH per ASHRAE 62.2 . Your house sounds like a sieve. Find out what the CFM50 was. A tight house is in the high hundreds while a leaker is into the thousands. I was in a super tight house once with a CFM 50 of 225. When a partnet slammed the door shut, the toilet flushed--no joke. Also inquire if they performed a Duct Blaster test on heating ducts, infrared thermography, or any energy calculations. Especially important would be a Worst Case Depressurization Test for backdrafting and CO.

What are their recommendations to lower your numbers and improve indoor air quality? If they haven't done anything to change the house then why do they want to re-test except to get more money from you.

Uni R_2

Thanks Bob

Good lead on the Infiltec!

I checked Infiltec, and they say divide ACH50 numbers by 20 to get the natural infiltration so that's not bad. I guess 5-6 is good and over 20 is bad. That's tighter than I thought and that was before replacing the windows and the natural draft boiler. It was a Canadian government thing where you get tested and they compute a score. You get one of them energy guide stickers. Then you do the improvements and then get tested again. You'd be eligible for a grant based on the increase in efficiency. I just couldn't get all the changes done within the 2 year time frame that they had. If I can confirm that the grant period has been extended I'll try and get retested by February. I still have 2 areas left for upgrading insulation, and maybe the front door as well and I still have to get my indirect functional. My score should be much higher.

Bob Harper

that ain't all that might be higher

With all your weatherization efforts, keep checking the venting to make sure you aren't getting CO. Classic trap, making it better makes it worse. Be careful.
Glad the links helped.

Mike Thomas_2

20mph

ACH50 simulates a 20 mile per hour wind on all sides of the house. CFM cubic feet per minute can be misleading when you compare a small home to a large home. The large home has more surface area, thus more area for leakage. Your number of 5 ACH is not bad. To get it any tighter you would probably have to rebuild it. I mean there is only so much you can do with doors and windows. To get the really small numbers you have to do a lot of sealing during construction and you are probably not going to tear your house apart to seal the areas that are left.