Question on air infiltration...

Softlite people talk about infiltration, I am wondering how important this really is for efficiency.

I can't find any studies on how much air leakage occurs WITHOUT the 25 mph wind which isn't going to consistantly hit a window 24/7 obviously. I am thinking it would be a tiny fraction compared to with a 25mph wind with no wind whatsoever, but actual numbers would be nice.


edit: also whoever locked my other topic and banned my other username "bensaccount", thanks. lol

Sorry about the previous post deletion. I can't really comment on that but it appears to be automated in some cases.

Air Infiltration (in my informed opinion) is 2nd only to U-Factor in terms of the overall performance of the unit.

I have done test-in and test-out blower door tests on homes that had window replacements and the difference (when the right window, installation, and procedures) can be significant.

The 25mph standard is the measuring baseline but I can assure you that there are pressure differentials that are driving air infiltration/exfiltration when the air is dead calm.

No worries. Ok well since an average original wood frame is .7, is .09 and .02 truly going to make that big of a difference?



How much did the blower door run you? How receptive are home owners to having a blower door test realistically?

I understand that their will be leakage from the differences in temperature and pressure etc but I don't see them being close to the A.I. number very often.

Appreciate the help I realize some of the info im looking for simply wont be available but every little bit helps me to get a better picture.

Air infiltration is very important and it also ( usually) is indicative of structural integrity .
So yes, pay close attention to that number.

The blower door tests were done to just get some comparative data and are not done as a standard with window replacements.

Will you notice a difference between 0.02 and 0.09, probably not. Will you notice the difference between 0.02 and 0.7, definitely.

Would loves to here more details on the blower door test. Were the new windows compared to the orginal windows or to other new windows?
Were other things done to the house for air sealing?

Todd,

Homes were the same model and build date. I would have loved to have gotten a customer to buy window "X" and then swap them out for window "Y" but it didn't seem practical.

No other air sealing was done as part of the process.

Previous windows where double pane wood with compression, vinyl jambliners. Not in terrible shape but far from great.

I only had baseline data on the home that we replaced the windows on and not on the home that got window "X". The baseline was 3,800 cfm at 50 Pascals. When we were done changing the 20 double hungs (medium sized 32 by 62 and a few larger) the blower door number was just under 3,000 cfm if memory serves me correct. That got us right into the upper part of the MVR and the customer decided not to do any additional weatherization at that point.

The other home was not our customer but they asked that we take a look and inspect the windows for proper installation because of persistent drafts.

Windows were installed properly (level and square) and did not appear to leak between the frame and home. They were not foamed in place but the gaps were small and windows were measured tight. I did not observe any air infiltration in that location on the IR.

The blower door number was just over the baseline of the previous home at about 3,900 cfm. The customer was complaining of drafts at the meeting rail and along the jambs.

We installed chimney blocks and weatherstripping corner tabs on all the windows for the client and it did drop the number a decent bit to about 3,700. There was still a good bit of infiltration noted via IR camera but that can be a bit misleading as you and I both know.

Feel free to email me offline and I can disclose the brands. I don't think that it would be right mentioning in an open forum and especially since I didn't do the install or have the baseline data.

Did the new windows get capped with aluminum or did just caulked in?

Coil.

Window install "Y" was doing with spray foam as well. Window "X" did not use spray foam but the gaps were consistent and supposedly caulked per the customer request prior to cladding the exterior trim.

My experience has been very similar to WoW's. In the past I was always very skeptical of the relevance of the air infiltration ratings once you get below the AAMA requirement of .30, but when my company added home energy audits, insulation, air sealing, etc to our suite of services, I was able to see first hand that there are some profound differences. As WoW explained, it is next to impossible to get the opportunity to test one brand new window next to another of a different brand with all conditions being equal, but we have replaced new construction windows that were only a few years old due to air leakage.
The impossible thing to do is to nail down a set number as a threshold for being good or bad, but you certainly cannot go wrong by going lower on that AI rating. Masterext's point on structural integrity is very valid as well, as I find that the units with lower AI ratings tend to have much tighter manufacturing tolerances. There are a few well made windows that don't have fantastic AI ratings for a variety of reasons, but there really are not many if any products that are of questionable quality despite a great AI number. It's a great way to gauge quality among units IMHO.