Hi all, 

I’m working on a remodeling a wing of my 1860 Victorian, including a primary bathroom. During this process, I am insulating and air sealing to the best of my ability, including spray foaming the roof line.

I am not spray foaming the walls, as the house does not have sheathing, and I would like to eventually re-side and add exterior insulation (distant future project). Instead, I will install r-14 TimberBatts and put SIGA Majrex over the exposed walls. The rest of the house has blown in cellulose in the walls. So far all of my renovations have shown no mold or rot on the backside of the clapboards, but my paint requires regular touching up from the vapor drive to the exterior. 

My question is: should I install an ERV in my old leaky house? 

I monitor the air quality and it usually stays pretty good except for when we cook, light candles, or clean. Also, our PM2.5 seems to spike during the heaviest commuting hours (we are close to the road). 

We do have rather high humidity in the house during the summers, so I worry that the ERV will make this worse. In the winter our humidity drops to 20-30%. 

We would pull air from both bathrooms and supply in a central hallway not far from the return for our ducted heating/cooling system. This should provide air to the upstairs where all the bedrooms are. For now, we will not be supplying any air to the first floor. 

Alternatively, we could install new bath fans only or consider a ventilating dehumidifier. 

Thanks for any feedback!