Makeup air strategies

[TommyMc]

I live in an older log home which we've been slowly renovating. Incrementally with each improvement, the house has gotten tighter. After our last renovations (larger bath, laundry, and new kitchen addition) the need for replacement air is becoming an issue. For the first time in over 30 yrs of running our wood stove as supplemental heat, this past winter we were plagued with poor draft and smoke in the house. Cracking a window helped...but defeated the purpose by letting frigid air in. Now in the warmer weather, we're getting a creosote smell when we run the kitchen or bath exhaust fans. It's clear that the easiest source of makeup air is down the chimney.

In researching solutions on the web, I find a lot of info about HRV systems which transfer heat from the outgoing air to incoming. I don't see any practical way of retrofitting existing vents like our range hood, I'm resigned to losing that heat....same as we always have. We ran one of those indoor analyzers last winter, which showed CO2 levels and particulate were ok when we weren't operating the woodstove. So I'm not quite so concerned about air exchange as makeup air. Is there some flavor of HRV that could mount in (for instance) the basement and condition incoming air and compensate automatically for the additional negative pressure when the vent fans and woodstove are operating? Is there a better strategy? Thanks for any insight.

 

[Fitter30]

ERVor HRV neither one will do what you want. HRV transfers some RH, ERV doesn't. Both the cfm in is the same as out. They also can go in a defrost mode id needed. Wood stove is decorative or sits in a basement? The make up air will vary with what exhaust fans are running. Baths and or kitchen exhaust and stove. Stove will vary with firing rate. A vane anemometer would help with how many cfm you need to make up.

https://www.amazon.com/Digital-Anemometer-Handheld-Accurately-Temperature/dp/B07J64TCBQ/ref=mp_s_a_1_3?adgrpid=1346903084271839&dib=eyJ2IjoiMSJ9.q5zGYT1ThIObSfri3KY8GZyMmEAYQaXJTCzyVRPpkK9OI_LL96N2Zk5rP3q2ccqQfsP3JaByesV-gkAdCG_ASG8GjncpMyJ_kWkEwNWL8-kWiaJeaRi_SuZwa5ksQCm12gTF4pSOMdlVxFnp8a2_JbUJYf9fuGnBbCpZhFwgfAm9T8C3tIjFI-dfTfZ0Ay-e8h9i71u5ZukNJQpG2HEG6w.j8BQK1CnXlN9HMXEB6uRCizpQybscbRRXIoOU_6-GP8&dib_tag=se&hvadid=84181635120227&hvbmt=be&hvdev=t&hvlocphy=85016&hvnetw=o&hvqmt=e&hvtargid=kwd-84182325909418%3Aloc-190&hydadcr=23922_13545957&keywords=vane+anemometer&mcid=4b7962d37620345089c9b9fe7e506a6d&qid=1748027100&s=industrial&sr=1-3

 

[Sponsor]

 

[TommyMc]

ERVor HRV neither one will do what you want. HRV transfers some RH, ERV doesn't. Both the cfm in is the same as out.

That's what I was wondering. It feels like I need an air intake that is sensitive to negative pressure and will also transfer some heat to the incoming air. The woodstove is "decorative" in the sense that it sits in the living room, but we typically burn 2 cords per winter as supplemental heat. The best DIY "woodchuck" plan I've come up with is to run a passive duct from the outside across the basement and through the wall adjacent to the stove. It would cool the basement a bit (unfortunately negating a lot the insulation I've put in the sill) but maybe pick up enough heat to prevent frigid drafts in the living area, especially while the stove is operating. Thanks for the idea of using a vane anemometer to determine how many cfm I need.

 

[Fitter30]

That's what I was wondering. It feels like I need an air intake that is sensitive to negative pressure and will also transfer some heat to the incoming air. The woodstove is "decorative" in the sense that it sits in the living room, but we typically burn 2 cords per winter as supplemental heat. The best DIY "woodchuck" plan I've come up with is to run a passive duct from the outside across the basement and through the wall adjacent to the stove. It would cool the basement a bit (unfortunately negating a lot the insulation I've put in the sill) but maybe pick up enough heat to prevent frigid drafts in the living area, especially while the stove is operating. Thanks for the idea of using a vane anemometer to determine how many cfm I need.

Have ever walked into a building where the doors or either hard to open or blowing open? That's build pressure. 36 X80 door has 2880 sq inches .01 pressure = 28.8 lbs doors hanging open pressurized can't pull it open handler.e. With a roaring fire and all exhaust fans on raising a window 2"- 4" could take some measurements and that would be worst case. The easiest fix a outdoor boiler with a water coil in your furnace or air handler. Might want to ask your electric company if they offer a energy audit with a blower door test to see how tight your house is.

 

[Josiah Barnabas]

Your house is just too tight now, so negative pressure is pulling smoke down the chimney. The easiest fix is a dedicated makeup air duct for the wood stove. A basement HRV can also help by bringing in fresh, conditioned air and balancing pressure when fans run.