Energy Myths

Comment

Comment by Danny S. Parker on November 28, 2011 at 3:31pm

Okay, I know the claim that cleaning refrigerator coils does nothing is wrong. Alan and the others should have measured more carefully. We have done so in several cases at FSEC and shown that the savings are about 10%-- mind you not enough to make it not worth replacing the frig if it needs it, but not zero for sure.

 

See "Refrigerators" and Table 7 in this evaluation:

http://fsec.ucf.edu/en/publications/html/FSEC-PF-339-98/index.htm

 

We have more data in even greater detail in a report yet to be released.

Comment by Ed Minch on November 25, 2011 at 6:28pm

Barry:

Just to open a discussion - on your blog with 10 myths you say:

Green building myth #4. Spray polyurethane foam creates an air barriet

 And in a list of things where it does not, you say "The crack between each pair of doubled studs"

 

This is s subject near and dear to my heart.  We have been sealing new houses using a bower door and scanner for guidance for 30 years, and we watched the insulators locally (mid-Atlantic) starat doing this about 1995 or so - they all started to do it at the same time for no apparent reason.  The New Jersey Energy Star for New Homes Program even insisted on this - and this was a major energy contractor who should have known better.  We just last Tuesday had a building inspector in Lancaster County PA tells us we had to do this - first time ever - and I feel we are successful in talking him out of it - we'll know next week.

I am going to assume that you mean 2 adjoining studs like you find next to a window or door, or the two double top plates on an exterior wall.

These pairs of studs or plates have a layer of sheathing - be it OSB, plywood, energy board - covering the crack on the outside right up to the window opening, and this material covers and will mostly eliminate any leakage that can get in between these members.  In addition, the required drainage plane on the outside of the house to keep water out of the structure further seals any possible leaks at these window or door members.  And the drywall on the inside adds one more layer of air sealing, in fact duplicating what any caulk would do.  

This does not apply to the pair of studs joining two wall panels in a panelized house, or the bottom plate of a wall sitting on a subfloor - these are certainly leaks and need to be sealed.

So a question;  Why haven't I seen these "problems" with an infrared scanner from the inside in completed new houses where we know we have not sealed them, or in exiting houses old enough to have been built way before the practice was started?

Inquiring minds

Ed Minch

 

Comment by Ed Minch on November 25, 2011 at 3:28pm

Jon:

We would all learn something if you were to take a blower door test before sealing all of these gaps and then again at the end to check for reduction numbers. Be sure the cover plate is on before the testing both pre- and post. Do the pre-test 3 times, starting from the beginning and zeroing out the baseline each time to check for consistency, and then 3 times at the end. Try to complete all work in as short a time as possibe, and maybe at a time when there is no wind and when temperature is not changing to get truly comparable pre and post numbers.  Try to do it in a typical house - here it would be a 2 story at 2200-2500 ft2 - and record the amount of time it took to do the work. This might add only a few minutes to do the testing as long as you are opening up these leaks to seal anyway. 

This would be a record of air leakage reduction overall, and therefore an indication of saved energy/money, but of course would not have any relationship to comfort.

Remember that it is hard enough trying to call what we do a science without basing it on anecdote.  Please let us know.

Ed Minch

Comment by Jon LaMonte on November 25, 2011 at 3:08pm

Another note on switch and outlet plates.  As I said before, every house is different.  I have also done pre and post blower door tests on homes with significant leakage at these plates and HAVE been able to show a difference.  

In the South, only drywall screws are used to attach sheet rock.  As the photo to the left shows, there is usually a large gap between the switch box and the drywall.  I actually had to clean a bunch of dirt out of the gaps on this one (a sure sign of air flow) in order to apply caulk to the gap. Couple that with band joists that leak like a sieve and no house wrap and you can get significant leakage.

So again, every home is different and in some, ignoring this issue would be a serious mistake.  The gaps behind the switch plates in the house I mentioned in the previous post were three times the size of the gaps in this photo.  Also, just applying a gasket without filling the gap around receptacle box with caulk or foam is a waste of time.  Its not going to stop all the air flow, but it will cut it down significantly.

Comment by Ed Minch on November 25, 2011 at 2:44pm

In 1984 we worked with the Air Force on making base housing units more efficient.  At the test base in NJ, we used blower doors and infrared scanners to be cost effective, but the base engineer kept insisting that the receptacles and switches were a major air loss.  The contract read that he had to do the pre- and post blower door readings, so we ran a test - in 2 of their 3 bedroom officers houses, 2 men spent about 45 minutes installing the gaskets and then the "childproof" caps with gaskets underneath.  The engineer could not measure a difference.  I have since ran that same test 2 other times with the same results.

I believe this is what happens: when drywall is glued (as it has been since 1980 or so in the mid-Atlantic), the glue bead is not continuous down the face of the studs - it looks more like morse code as the installer makes a swift motion while pumping the handle of the gun.  When the drywall is installed, there are a series of spaces with glue and a series of spaces without glue.  And when there is no glue, there are plenty of side-to-side air spaces.  So air is free to travel left and right in the wall from stud bay to stud bay through these spaces, as well as wire holes, etc. In addition, there is usually no glue along the top plate, so air gets in there, even on first floors of 2 floor houses since the band between floors is leaking.  So air is free to get from the northwest corner of the house to the southeast corner of the house in the walls without entering the house.  When we gasket the receptacles and switches, we have merely chased that air leak to another location, end result being no result. This is why we see air leaking out of receptacles on an inside wall on the first floor of a 2 story house.

There are certainly locations where you WANT to chase the leak - the receptacle on the north side of the house that blows cold air on the owners shin when he crosses his leg to read his newspaper after a long day - but understand that you have saved no energy.

And 2 years ago during our BPI QA, we were told that not installing receptacle gaskets was a "missed opportunity".  I took it to mean a missed opportunity to waste time.

Ed Minch

Comment by Jon LaMonte on November 25, 2011 at 6:54am

Good article.  Most of this is common knowledge to energy pros, but I guarantee your avg homeowner would be surprised by some of the these "wives tales" debunkers. It amazes me how much time I spend being the "debunker".  Even more amazing is the look on homeowners faces when you tell them the idea they have kept sacred for years is wrong.  Do they believe your or not?

Some improvements even though they might not yield great energy savings, can contribute to an improvement in comfort.  Making sure that the homeowner knows the difference is the key.

Also, in relation to the air leakage from the switch and outlet plates, every house is different.  I was in a home during a very windy day, and every time a high gust of wind blew, air came flying out of the switch plates. There is a way to address these properly (not just plopping in a useless gasket) so that it contributes to both comfort and energy savings.

Comment by Christopher Cadwell on November 22, 2011 at 6:42am

Hahaha - What about comfort?