Comment by nehal3m
6 hours ago
>One solution that can help is an external air heat exchanger
I have one of those, it blows fresh air in through the bedroom and sucks it back out through the kitchen (loft house, this route prevents food smells from wafting into the bedroom). Aside from just feeling fresh all year, this system also prevents mosquitoes from entering in summer while still allowing air circulation, it automatically bypasses the exchanger at night to provide cool air and it has some pollen filters installed which helps with hay fever.
So great economic return and a bunch of upsides, but it does require space for the exchanger and the ducts throughout the house.
This. I have that type (regenerative MHVR) installed in the attic for upstairs, and a synced pair of in-wall ceramic (recuperative) types on opposite sides of main living area downstairs (eliminating ducting, albeit with reduced efficiency). I haven't attempted any energy/ROI calculations but fresh filtered air, lower humidity and good nights sleep are well worth the claimed single-digit watt power usage to me.
I suspect bathrooms aren't big enough to buffer the air pressure but it seems like we should design the air handling so the “fan” is always on in the bathrooms. Maybe a split between several places and taking a bit from the cold air return for the rest.
The system is always on as a whole, and the water closet and bathroom have an intake duct that sucks in humid air that goes to the heat exchanger for exhaust. I have a little humidity sensor hooked up to Home Assistant that kicks the fan in the exchanger into a higher gear and returns to auto when humidity returns to baseline.
All rooms in the house have an intake or exhaust duct depending on requirements.
There is also a small control panel next to the thermostat in the living room that controls the whole system for when, ahem, your number two's are particularly odorous (or you're using the kitchen to cook for 6).