Blower door on a new addition: suggestions?
I would like to perform blower door testing while performing air sealing on a new addition to an existing home. This addition is not connected at one point by a single doorway, of course, it is more of an open plan configuration. The existing part of the structure is old and leaky (air wise). Air sealing and energy improvements will have to come later to this part of the house (not my own).
Since isolating the addition would be very difficult, what would be the blower door strategy? Is the only hope to take a lot of time to construct an isolation barrier for the new addition? Should I test the entire house prior to construction and perform some quickie air sealing on the existing, then build the addition and seal with the blower door before drywall?
I want to be sure that the new addition is tight, and that the addition can be eliminated from concern for future blower door testing and energy improvements. I am considering getting my own blower door prior to this job, it just seems inevitable that we will soon have that in the truck, right along with the table saw.
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If you can't isolate the addition with plastic sheeting and tape, you can't test it separately. That doesn't stop you from blowing the whole house at once, and doing your air sealing--if you can get -50 or close to it, that's plenty for guided air sealing. I can almost guarantee you that once you have the fan running and see where the leaks are, you will want to address the whole house.
David,I'm wondering if a blower door would even be necessary at that point.I am sure that I could generate plenty of negative pressure to guide air sealing ( we have negative air machines for dust control).We also have fog machines (for other purposes) if we wanted to turn the NAM around and pressurize.I have not air sealed before.Would it be helpful to get some measurements via blower door right from the beginning for comparison's sake,even if it were to supply some info to the client?
You could certainly go ahead with the NAMs as your fans, just make a piece of plywood with a hole in it for the outlet duct, so you can minimize incoming air where the duct goes out of the house. I would probably invest in a smoke pencil, or just use your hands to find the incoming air. I haven't done a house with a fog machine, but I have heard of people using them outside when the house is negative, and or course inside when it's positive.
Dennis,
For more information about testing for air leaks with a fog machine, see Pinpointing Leaks With a Fog Machine.
For more information on using a blower door, see Blower Door Basics.
David,thanks,any suggestions for the smoke stick?
Is there an advantage for actually measuring the ACH,right from the start of the project,or just do the air sealing very well and move on.David,I would certainly continue on to additional air sealing in the home,if everything is agreeable.Where would the quickest,easiest gains come from in existing 1950s construction?
I have a Regin smoke stick and like it. The smoke is non-irritating, at least it has zero effect on me. There are a few other types commonly used by folks who do air sealing, one of them is the Wizard Stick (?) and doesn't need lighting, it has batteries.
I think you need to be able to measure ACH50 at some point in the project, definitely at the end, so that you can determine ventilation needs. I wouldn't blindly air-seal a house. IMO it is prudent to understand the various ASHRAE standards and know how to apply them. If you have a blower door and software it will automatically tell you what the recommended levels are. Or, google for an ASHRAE 62.2-2010 calculator online, I believe there is at least one. You seem like a good candidate to just buy a blower door, since you are doing the work for others as a business. The only caveat would be if there are already dozens of guys running around with them in your town. Here there are not, so I bought one and it was a great investment.
There are lots of possible air leakage sites in a house, and the easiest/best thing to do is simply run a fan and start finding them. After an hour or two of room-by-room investigation you will have a very good picture.
One more thing... if you really want to go the whole 9 yards, you need to buy a device to measure exhaust fan flow, so you know if the exhaust fans are doing enough to meet ventilation needs. Take a look at the Energy Conservatory site for the various tools they have. Retro-Tec also makes everything you need.
In my opinion the ideal BD setup, although likely not feasible as a homeowner as it requires 2 blower door setups, would be to conduct a pressure-balance test, sometimes known as a "Guarded" blower door test. The concept is to separate the existing from the new with a temporary air tight partition constructed along where the new meets the old and to depressurize each space together until each side reaches -50pa. The theory is that with each space equally depressurized you mitigate any air flow between the two spaces and can isolate your addition enough to take a fairly accurate CFM reading of just that space and its exterior components. I've created the partition in the past by building a quick frame with poly on at least one side and taped along the seems with painters tape.
This process works but is time consuming in set up and in testing. If the rooms aren't slowly and equally brought to -50 pascals your sealing job at your temporary wall may fail, and you will have to reseal and start the test all over.