Mech. Ventilation in new construction
I am building a new 2 story 1400 sq ft earth advantage home and need help determining the best way to vent it (through a ceiling mounted bath fan). Heat system is ductless minisplit. Slot vent windows are the only fresh air inlet, I want to use my bath fans to pull in the fresh air.
Questions are…
-Should I have continuous venting fans in both bathrooms? (1st and 2nd floor)
-Panasonic and others make a fan that mounts in the attic and runs seperate ducts to the bathrooms..is this a better solution?
-Should I buy the fans that have built in timers or just wire them to my own 24 hour timer? It seems like the 2 speed fans would be good for continuous ventilation.
Thanks for any insight
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Replies
J.P. Eaton,
There is no single answer to your question.
It seems that you want to install an exhaust-only ventilation system. While this is one option, it is not the only option. You may want to consider installing an HRV or ERV.
An exhaust-only ventilation system can be controlled by a timer, as you suggest. In some cases, a small exhaust fan can be set up to run for 24 hours per day, although this can result in overventilation.
In all cases, you need to calculate the required ventilation rate to determine the programmed run time of your fans. Most people ventilate at the rates suggested by ASHRAE 62.2, although some homeowners prefer to ventilate at a higher or lower rate. Remember, ventilating at a higher rate carries an energy penalty.
Here are two articles to provide more information on the topic:
https://www.greenbuildingadvisor.com/green-basics/ventilation
https://www.greenbuildingadvisor.com/blogs/dept/musings/designing-good-ventilation-system
Panasonic bathroom fans are what I use to ventilate my superinsulated homes. I put them on short-term push-button timers within the bathrooms that are used when showering (or removing odors) and on 24-hour Grasslin programmable timers (the analog, dial units - the electronic digital units won't work) that are located outside the bathrooms and which are programmed for the required number of hours at the measured flow rate (or calculated rate with duct resistance included) to achieve 0.25 air changes per hour average over a 24-hour period.
I would not recommend the central ducted exhaust fan as it's more economical and functional to run spot ventilation only in the bathroom being used, while setting each bathroom timer for the air volume required for that floor.
An exhaust-only ventilation system, however, requires passive make-up air inlets, like the American Aldes Airlet 100s (which is my prefered unit), strategically located in each bedroom and in all living areas sufficient to make up the exhaust flow of the fans.