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Power damper in basement hopper window?

tastydonuts | Posted in Mechanicals on

Has anyone attempted to retrofit a power-open damper to a small basement hopper/block window? I have a natural vent steam boiler in my basement. After a full remodel I will be relying on it less as I have improved insulation and air sealing, and added a multi-zone Mitsubishi HyperHeat system. But I will still supplement with the steam radiators when the temp drops below freezing, both for comfort and to ensure the exterior walls are sufficiently heated to prevent freezing of the exterior brick. The home has withstood Zone 5 winters in exemplary condition for nearly 100 years for a reason!

The boiler is in a large unfinished basement, so code doesn’t require any makeup air. I could leave it as-is, but with multiple exhaust fans (5x 80cfm bath fans, 400cfm range hood) added throughout the house, with no makeup air provided there’s greater potential for negative pressurization so I’d like to eliminate any risk of  backdrafting. Ideally I would run an insulated intake duct to the base of the boiler, but that might be unwieldy. So I thought I’d just put a damper on a window, and wire it to the same circuit as the boiler’s exhaust damper. I realize this will make the basement considerably colder when it’s operating, which will reduce efficiency and introduce some condensation risk on frigid days. Not sure if I’m just substituting one problem for another… any other clever ideas to deal with natural venting in the basement appreciated!

P.S. Fortunately this is the last natural venting appliance left in the house. I’ve switched the range and clothes dryer to electric, and the two other boilers (DHW and radiant floor) are direct vent.

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  1. walta100 | | #1

    My guess is it is that snow balls have better chances in hell than you have of finding and sealing all the leaks in your old house to the point of back drafting the boiler.

    Have you gotten a blower door test result under 1.5 ACH50? Without the blower door test I think you are fooling yourself because old houses just have so many leaks big and little in impossible to access locations It is very unlikely you could have gotten enough to create the problem you are wanting to fix.

    If you have not had a blower door test, consider blower door directed air sealing done.

    If the boiler did backdraft your CO detector should sound well before it could be a problem. Having at least 2 CO detectors is always a good idea.

    If you are still unconvinced turn on all the exhaust fans and hold a burning incense sticks in the boilers flue and see if the smoke comes back into the house or go up the flue.


    1. tastydonuts | | #2

      That's very fair, I should just do the blower door test. :) While the house was surprisingly comfortable (not drafty) in most rooms before I did anything, I doubt I'm even close to 3 ACH50...

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