Greetings everyone, 

    I did an energy audit on this new home that is too tight and needs mechanical ventilation, so I thought to tell them to get an ERV installation, but then I realized that they are heating with radiant floor heating, so there is no ductwork at all and to make things more complicated, there is no attic.  To make things even more complicated, the bathrooms does not have fans, and the kitchen fan does not exhaust to outside... so I was thinking that because there is no attic, I would had no choice but offer to install the bathroom fans independently from any ERV install since there is no attic that would allow some kind of duct work installation, I going to recommend to vent that kitchen exhaust outside, but then, how would the ERV be install? 

   Your advice is greatly appreciated, 


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Just a few thoughts & I am basing this on dedicated exhausts with an E/HRV (that may or may not be running at the time) also being used. Let me also state that like many things it depends, sure one model might have, or I saw a house where... this is an overall look based on numerous climates 

The fan will depressurize the house forcing everything to come through the walls - not even close. Reality has shown that air comes from the path of least resistance & more often than not that is the ERV. Sure it won't be exhausting as much air when the fan is on, but at least it is filtered.

Shared core - what just worried about odor's? Well I know a few that are saying that when Uncle Tom comes over... diluting it a million times probably wouldn't be enough. In all seriousness though there are a few issues:

Trapped grease on the filter from kitchens, not only blocking the filter but depending on the items cooked could be leaving the house permanently smelling like...

Water vapor - not all is exhausted which might not be a big thing during a cold winter, but that is not the best thing for all climates nor all times during the year.

Playing devil's advocate - what happens if something starts growing because the temps are always nice, the customer loves taking long hot showers i.e. moisture content is there & yes even food sources are delivered? Guess what will also be flowing back into the house also  

As for comfort - with the exception of maybe some homes in the NW that are using ERV's only for delivering heat to bedrooms or some PH - the customer is not going to notice - the comfort is from the HVAC system. Drafts - that is either air leakage or standing to close to a window when it is cold out 

The only thing the ERV/HRV really is for is air quality & that is derived from the filter as the "fresh" air from outside isn't always that "fresh"

Very good reading. Thank you for posting this.

Rather than recommend an ERV, how about some thru wall exhaust fan(s) in the bath room(s)? Put them on timers so they don't run all the time.

That kitchen fan REALLY needs to exhaust outside.  I would make that a higher priority than the bathroom exhausts.

So why go balanced instead of exhaust only? Well you might want to review the piece I linked to at the start & then also the one by William Nickerson above. One big thing to remember is location - you don't want to be pulling hot humid air through wall cavities with AC

As for priorities - maybe. Do they even cook, if not then bathrooms definitely take priority as everyone uses them ;) now of course do they use the fans at all... In reality baths always are above kitchens unless they are doing Indian cooking or are needing hi exhaust fan rates which opens up another cans of worm for another thread

Yes do do cook and the stove is a gigantic Viking commercial stove! There is no AC on this house, but I still agree with you Sean, it should be a balance unit.

How is it possible that there is NO ventilation in this house. How could it have it passed a final inspection by the building dept.!

This is crazy!!

In my humble opinion I think the inspector got fooled because he saw fans... there are just not venting to the outside! What makes things worse is that the house is too tight so there needs to be mechanical ventilation as well!


I would install a balanced ERV. You need to exhaust the bathroom and kitchen to ASHRAE 62.2 and install supply to the bedrooms and other living areas.

Yes it would be an independent system with duct work, and you would need to get creative on the location with the homeowner.



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