[Greenbuilding] Fresh air to boiler questions

[Norbert Senf]

On Wed, Jan 14, 2015 at 4:36 PM, Benjamin Pratt <benjamin.g.pratt at gmail.com>
wrote:

> Norbert, I would love to close off that 6" hole. I was told that the
> boiler would operate less efficiently if I do that. I suppose that assumes
> less oxygen
>

not true, common fallacy. In some jurisdictions, building code may require
it, or it may be in "manufacturers installation instructions", so you need
to check that.
Only exception I can think of is a separate, sealed, furnace room. Always
make sure you have a CO detector, since low level CO spillage is very
common with your type of setup, outside air or not.


> IF that is not true, I and am ready to plug up that hole! Any ideas about
> the open flue of the boiler and the water heater? Are they less concerning?
>

Not sure, since my experience is with wood and not oil or gas. In a
basement, you are very likely to have negative pressure, so on standby
perhaps there is not a lot of flow from the basement into the barometric
damper, particularly if you have an outside chimney. If you take a sheet of
old style newsprint, it has a grain orientation to it, and in one direction
you can tear it into parallel strips. This makes a handy flow visualization
tool, for example low flows into open fireplaces. It might be interesting
to check around your barometric dampers, air inlets, window drafts, etc. A
stick of incense, or a cigarette, is good also ;-)


> Thanks!
> Ben
>
>
>
>
>
> b e n j a m i n p r a t t
>
> professor art+design
> the university of wisconsin stout
>
> On Wed, Jan 14, 2015 at 3:04 PM, Norbert Senf <norbert.senf at gmail.com>
> wrote:
>
>> 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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>
>
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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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