[Greenbuilding] Fresh air to boiler questions

[Norbert Senf]

The air consumption of an 80,000 BTU/hr boiler is in the range of 25 cfm
while it is operating. Heating that combustion air by 50 degrees F requires
about 3,000 BTU/hr, which happens no matter whether the outside air has a
direct or indirect path to the burner.  Having a 6" dia permanent leak in
the basement is a really inefficient way to do it. There is no good
engineering reason to have that leak, unless your basement is hermetically
airtight and 25 cfm would depressurize it enough to cause the boiler or
water heater or (worst case) an open fireplace to backdraft. This is
generally considered to be -5 Pa. Much more likely that a 250 cfm kitchen
exhaust hood would do it, assuming that your basement is not sealed from
the rest of the house. Clother dryers and bathroom fans also, are in the
100 cfm range.

On Tue, Jan 13, 2015 at 7:43 PM, Benjamin Pratt <benjamin.g.pratt at gmail.com>
wrote:

> I have been sealing up and insulating the unfinished portion of my
> basement, but am concerned it is a waste of time and money: There is a 6"
> fresh air duct to provide proper combustion for the boiler. Also, there is
> no damper on the water heater or boiler. Therefore, a lot of cold air is
> continually dumped into the basement, and a lot of hot air escapes up the
> chimney.
>    I suppose the solution to this would be to install a new boiler, and to
> install a direct vent kit on the water heater. The boiler is around 15
> years old, and is 84 percent efficient. If I buy a more efficient boiler,
> that is direct vented, any guess as to how much energy I will save? I
> suppose its more then just the amount of natural gas I will save with a
> more efficient boiler, since I would also be eliminating a huge source of
> air infiltration. I would like to be able to calculate the ROI, so my wife
> agrees to the purchase.
> I'd appreciate any help you can provide.
> Thanks,
> Ben
>
>
>
> b e n j a m i n p r a t t
>
> professor art+design
> the university of wisconsin stout
>
> On Tue, Jan 13, 2015 at 3:46 PM, Sacie Lambertson <
> sacie.lambertson at gmail.com> wrote:
>
>> I'm looking for an architect in Seattle who understands energy efficient
>> good building and does contemporary design work.  Welcome suggestions.
>> Best to send these off the forum, to me directly. Sacie
>>
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-- 
Norbert Senf
Masonry Stove Builders
25 Brouse Road, RR 5
Shawville Québec J0X 2Y0
819.647.5092
www.heatkit.com
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