Test your negative indoor pressure for free

[danham]

We just had an energy audit done on our house as part of upgrading our HVAC system (it sure was nice to have wood heat for the 2-3 days the furnace was out of commission). The company normally charges around $200 for the audit, which took about 3 hours, but our gas company (National Grid) picked up the tab as part of the MassSave program (Massachusetts).

Part of the audit involved putting a very sensitive meter in a basement window and running every possible source of negative pressure -- 2 bathroom fans, clothes dryer, furnace air handler. The result, measured in Pascals (Google it) was about negative 5. Turning off all those sources of negative pressure left us with a "natural" convective draft of around 1 Pa. Moral of the story is that seemingly small items like the bathroom fans move a lot of air away from your stove's intake (unless you have an OAK). Oh, and with an energy audit, possibly subsidized by your utility, measuring it is free.

-dan

 

[EbS-P]

5 pascals is 0.02 inches water column. For anyone interested

Edit. Remember at these low pressures (probably less than 5 pa) it’s not uniform across the whole structure.

Any HVAC system running will change local room pressures by more than 5

 

[danham]

5 pascals is 0.02 inches water column. For anyone interested

Thanks. Not being familiar with Pa units, what struck me most about the test was the difference between fans on and fans off. Figured this might be useful for folks in this forum with draft issues.

-dan

 

[Eman85]

I had TVA come out and do an energy audit. They did nothing and gave me a pack of LED bulbs that don't last.

 

[EbS-P]

I had TVA come out and do an energy audit. They did nothing and gave me a pack of LED bulbs that don't last.

Duke did the same! But now I can get a blower door test for like $60. I’ll get one scheduled this summer when the stoves are out and cap the liners before hand

 

[stoveliker]

These tests only make sense to do if you either have problems with a wood stove, or you're planning to actually do something about any negative pressure (if already tight, ERV or HRV, if not tight yet and natural convection, then tighten up the home).

My $0.02

I havent done one because I know everything but the ceilings to the attics and my windows is not tight...

 

[danham]

These tests only make sense to do if you either have problems with a wood stove, or you're planning to actually do something about any negative pressure (if already tight, ERV or HRV, if not tight yet and natural convection, then tighten up the home).

My $0.02

I havent done one because I know everything but the ceilings to the attics and my windows is not tight...

True, but it was a requirement to get rebates/incentives when replacing our HVAC system.

-dan

 

[stoveliker]

Yes, I understand. That's a very good reason.