I am interested in getting a blower-door test performed on a house that I have under construction in Salida, Colorado (framing is just starting). I would like to do the blower-door testing after the windows and doors are in, but before insulation and sheet rock are installed, so that I can get to the leaks and seal them up. One problem that I am aware of is that the normal air barrier is the sheetrocked ceiling, but it will not be in place. There will be continuous soffit vents (Hardie vented Cedarmill panels) and a ridge vent (Cobra exhaust vent - rolled material) that will leak air. Plastic sheeting duct-taped on outside of the soffit vents might work to roughly seal them, with the vaccum drawing the seal tighter. How about duct tape over the 3/4" wide Cobra exhaust vent material from the outside and hope the vacuum helps seal it? Thanks for any ideas.

No Prob...at that time in construction, you're not really interested in a final ACH figure, just identifying leaks. Try to seal what you can and concentrate on sealing those areas that will no longer be exposed after insulation & drywall. Keep in mind that as large leaks are addressed, smaller leaks are exposed. If one fan is not sufficient to adequately depressurize, borrow a second & use them both. I think your efforts are smart & should be done more often.

Thanks for the ideas and help.  I will see how many fans I can line up for the testing.

Are you planning on doing another blower door test later once the insulation and sheet rock are installed? This test will give you a good idea about your major problems, but I'm not sure that even two blowers would be able to catch the smaller leaks that you might find once the drywall and insulation are in. You might try to rent a high capacity squirrel cage air blower, one with a 3-5 Hp gasoline motor and a 12" flexible hose like they use to dry up areas after floods. Those things can move a LOT of air. Since you don't need the measuring capability with this first rough test, you could really just make a plywood template for a fan like that that would fit into a window and tape it tight.

That is an interesting idea.  Not sure if they are available in the small town where the house is being built, but I will check into it.  I did a quick search on the internet and in Grainger catalog for these devices in general, and did not find them, but I will look further.  Thanks.

You can also use an abatement fan used for demo / asbestos, a 2,000 CFM unit moves a lot of air.

http://www.abatement.com/asbestos/e...bestos.htm

I've heard of people using fans like this as well in a sheet of plywood as aardvarcus described: http://www.shophmac.com/j-and-d-man...s161c.html

guys
I'm really interested in doing this. I have all the framing in place. getting ready to insulate. How does this work? I have an attached garage. Wouldn't all the air go out the garage doors?

Yes. It will take some time & lots of plastic to get it sealed well enough to use the BD & see results. There may be also vent channels in the eaves (or open eaves at this point) which will be harder to seal up. If you can spend the time to do this it will be benefiicial in the long run.

Since you're ready to insulate you could hang drywall on the garage wall (and up to the roof) so you'll just have the doorway to seal; that way the garage would be outside the envelope and you'd have fewer air leak possibilities.

thanks Bob. Should i do the house as 1 unit or should I do every room separate?

Since you don't yet have drywall up it would be difficult to separate every room. I'd suggest dividing the house where ever you can do it fairly easily - perhaps at a stairway if it is two levels.