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Ferndale, Wa
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Gaston, Oregon
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 New energy Code
[#2] Posted: 04/28/2012 - 12:26:49 PM |  |  |
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Kirk,
The SLA is a ratio. It represents how much air leaks out of the building per square foot of conditioned area when the building is pressurized to 50 pa. It's necessarily a very small number. The fact that the number is very, very small does not necessarily mean that the building is very, very tight. (Think about it this way: my car only weighs a few ounces per square inch. Do I have to be worried that it will blow away in the wind?)
The energy code blower door test results produce numbers that are meant to be compared with the numbers from other houses that are tested in the same way. The test conditions are artificial and don't necessarily correspond with functional day-to-day performance. They have NOTHING TO DO WITH ventilation requirements, which are in Section 1508 of the WA State Building Code. (Which contains full provisions for outdoor air inlets.)
You can't take the SLA, and reverse math it to come up with ventilation requirements.
If you want to find out if a house is properly ventilated, go to 1508 and use that. It tells you that if you have a house with X square feet and Y bedrooms, then you need a ventilation equal to B, including a prescriptive amount of makeup air from the outdoors. None of it is related to the blower door test.
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Jim Katen, Oregon
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Kenmore, WA
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New energy Code
[#3] Posted: 04/28/2012 - 1:20:40 PM | | |
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Quote: Originally posted by tybertown29 Some of you are aware that the new 2009 Washington State Energy Code that went into effect January 1, 2010 requires new construction to pass a blower door test and a duct test. The code requires the building to pass a leak test (SLA where SLA= Specific Leakage Area) of less than .00030. Unfortunately they do not give you the measurement (square inches, square feet or square yards) at any rate I have inspected a few of these houses where the test is done and is posted as per the code. However when I do the reverse math figure out how much CFM they are leaking I am getting a little concerned. I see tests that pass with a SLA of .00020. Now regardless if it is square feet, inches or yards when you are getting into the 10 thousandths you are making a pretty tight house and when I do the reverse math it requires full mechanical ventilation to make of the Building air flow standard of what the Building Performance Institute Requires. Now this all begs the questions of what about ventilation? Still just relying on the little whole house fan located in the laundry room that runs off the timer that rarely gets set properly. Also how do you pull air on a house that is that tight without leaving open a window? Any thoughts comments or concerns with what I am seeing???
This was the very reason I objected to our board trying to assert any kind of jurisdication/control over energy auditors when some members decided that since x-number of things were being looked at by energy auditors they must therefore be performing defacto home inspections. I don't think we have any business going down that path. I have no objection to someone adding an energy auditor revenue stream to their business, as long as they don't go around representing that doing so is part of a home inspection, because they are two different animals and I think they need to be kept that way.
Once you start doing that, when do you not do it? Are you going to sit there with a calculator on every single house to try and determine whether someone else's math is correct? If you're going to do it for an energy audit, why not do manual J calculations while you are at it to determine if the heating system is properly sized? Why not take the time to check the data plate and wattage on every single appliance and then sit there and do a load calc on every single house? Why not measure the size of every window and wall in the house to calculate whether the builder has kept the ratio of window to wall space within specs? How about when you are doing old houses with questionable insulation or no insulation in the walls and loose construction? If you do it for new homes and report it as part of your home inspection, shouldn't you be doing it for those homes too? Just how slippery a slope do you want to walk on?
There are certain things that the AHJ is supposed to do. One of them is making sure that the blower test was done and the results are posted. We have no requirement here for you to confirm that the blower test was done, that the results are posted or to double-check anyone's math. It is essentially a get-out-jail-free card for inspectors where inspectors can easily bow out of getting hooked into the energy efficiency quagmire and can stick to reporting what they see in front of them instead of trying to predict with a slide rule whether someone is going to be spending too much money down the road heating the home to that person's personal taste.
Just my opinion; worth the price charged.
ONE TEAM - ONE FIGHT!!!
Mike
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Gaston, Oregon
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New energy Code
[#4] Posted: 04/28/2012 - 5:12:22 PM | | |
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Mike, what makes you think he's asking this in relation to a home inspection?
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Jim Katen, Oregon
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Friday Harbor, WA
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New energy Code
[#5] Posted: 04/28/2012 - 6:16:40 PM | | |
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| Quote: Originally posted by tybertown29when I do the reverse math
The WSEC SLA = A / B, where:
A = measured CFM50 * .055
B = square footage of house * 144
As you say, the code standard is .0003 or better.
So, a house that's 1500 square feet needs to hit 1178 CFM50 or better.
If that house has 8 foot ceilings, it has 12000 cubic feet of enclosed space, and at 1178 CFM50 would have 5.9 ACH50. That's not all that tight, and in my experience it's approaching the point where the owner is likely to have some comfort or energy bill complaints.
If the same 1500-foot house has 9 foot ceilings, it's still over 5 ACH50...
IMO if you're doing these tests, or an blower door tests at all, you should be giving the owner a printed report that discusses the ventilation standards. Most houses have enough bath fans and a laundry fan already installed to meet the ventilation requirements, if they're needed for that purpose.
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Kenmore, WA
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