Small house ERV options
bradse
| Posted in General Questions on
I’m building a small 900 SF cabin in Northern Wisconsin and trying to figure out what makes sense for ERV / HRV and bathroom exhaust and kitchen exhaust.
Its slab on grade construction with radiant heat in the floor. I’m planning on leaving the floor heat set to condition the space to 55-60 degrees in the winter and then using a mini split to bump the temp up when we are there mostly on weekends.
Any recommendations on ERV / HRV for a small space like this? Should the bathroom exhaust and kitchen exhaust be tied into one system?
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Replies
900 square feet is large enough for a traditional ERV. If it were my place, I'd use the ERV as the bath fan. The general recommendation when using this strategy is to size the system based on square footage and number of bedrooms (both building codes and AHSHRAE 62.2 have ventilation rate recommendations), then double it. When setting the ERV CFM rate, set it to normally operate at the recommended rate for the size and number of bedrooms, then use some sort of switch in the bathroom to boost the system while the bathroom is occupied. It's not recommended to use an ERV or HRV as a range hood, but you can install an exhaust vent from the system in the kitchen, just keep it away from the range. If you wanted, you could also place a boost switch in the kitchen as well.
A couple other pieces of advice, if you are using a non-auto balancing unit, make sure the unit gets balanced. These systems will have unbalanced flow rate because of duct design and style of terminations used. If not balanced, the home will become positive or negatively pressurized. Some of the newer systems have auto-balancing capabilities, personally, I'd choose one of that style.. Also make sure to follow the manufacturer's recommended maintenance schedule. The self-balancing units will keep the home under a neutral pressure, but if a filter or intake duct becomes plugged, the system may throw an error code and stop working.
That all makes sense. Appreciate the info!
I'm starting a small house build too and I'll be using Panasonic intellibalance 100 with external 14x14 Merv 13 filters.
I plan to put the supply into the 2 bedrooms and return from the living room that way the whole house is ventilated.
The kitchen will have a 900 cfm range hood and the bathroom will have a separate 150 cfm exhaust
Why not split the stale air pickup and run one to the living space and one to the bath?
This would let you skip the bath exhaust fan. One less hole, one less part to install.
The flow rate might feel on the small side but don't forget this will be running 24/7, that will move a lot of air especially in a small bath like that.
Keep in mind that the fresh air supplied by the ERV will be a bit colder than house air in the winter and warmer in the summer. Make sure you get good mixing inside the bedrooms so you don't notice this. In very cold climates, a post heater element is a good idea on the supplies.
Hmm I hadn't thought about that option akos but I'll give it serious thought.
At first glance it seems the exhaust would bypass the living room since the bathroom is so much closer to the bedrooms.
Maybe I could do a supply to the living room(3 supplies) and the return in the bathroom.
Will definitely consider this.
btw, here is my floorplan. very similar to yours
https://i.imgur.com/qEcgAfX.jpeg