Would this work?

I have the plans for a house that goes one step beyond the massive "commercial" stoves that seem to be routinely spec'd in new houses. The cooking area is 9' long and consists of a 36" gas rangetop, 24" elec griddle, 12" fryer, 12" 15k btu wok burner.

There are two 4' hoods over the cook area. The architect specified remote mounted  3 speed 600-900 cfm fan to vent the area and another fan same size interlocked to supply make up air to the A/C system. Since its an A/C only system electric elements are required to heat the air.

I have been looking at commercial HRVs that move the same amount of air. One manufacturer (on the residential side, not sure on the commercial side) suggests exhausting kitchen hood through the HRV if and only if a suitable grease filter is used to capture grease prior to entering the HRV. 

Given that the cost of a commercial HRV of the appropriate size is in the neighborhood of the spec'd system. I would like to get some opinions on whether or not this arrangement would work.

Construction is very tight two story ICF with SIP roof and very careful detailing of all infiltration points.

Even with a grease filter on it I'd expect an HRVs core to lose heat exchange efficiency pretty quickly if you're doing a lot of cooking- no grease trap is perfect. Unless you're running your home kitchen at a very high duty cycle, the amount of money you'd be saving on heat with that heat exchanger would be pretty minimal even if the grease COULD be fully eliminated. But with even 0.5% of the grease getting by the filter, with the increased maintenance/replacement schedule, an HRV on that path wouldn't likely to ever be cost-effective. If you're not running it less than 3-4 hours/day (every day), an exhaust-only vent scheme becomes a "who cares?" level of heat loss. Only during the real peaks of the heating & cooling season would that HRV be buying you anything.

Pre-heat on the makeup air is also not likely to be necessary for comfort unless it's well below 20F outside. Earth-tempering the makeup air path to the AC and whole house HRV (PassiveHouse style) is likely to be make a bigger overall annual energy use difference than an HRV on a kitchen exhaust. During the summer an HRV on the kitchen exhaust vent would even be ADDING to the air-conditioning load (not much of a problem if you live in Whitehorse Yukon or Nome AK, I suppose... ;-) )

Spending the money elsewhere- drainwater heat exchanger on the main shower, under slab insulation, better foundation insulation etc are more likely to have a payoff, as in "NPV positive rather than negative a 20 year financial analysis".

You might find this discussion useful:

http://www.greenbuildingadvisor.com/blogs/dept/building-science/can-kitchen-downdraft-fan-be-connected-hrv

http://www.greenbuildingadvisor.com/community/forum/general-questions/15959/kitchencook-top-ventilation-passivhausleed-home

Seems for smaller-duty kitchens a grease-trap filter on a non-exhausting vent might work for a non-gas-fired cooking, letting the whole house HRV handle the humidity. But that would never meet code for gas-fired appliances. With the peak levels of gas-burning this kitchen will see, exhaust-vent it and forget it.

I agree - no ROI on a HRV. I'd use dual fans in a push/pull configuration in the stove area to keep the house pressure neutral and minimize the conditioning needed. Ie, outside air would be blown in, pass through the stove top area, then up and out via the exhaust fan/hood.

Thanks for the responses. I never stopped to consider NPV.

How would the push-pull configuration introduce the outside air? Down by the countertop on the sides of the cook area or does it need to be distributed accross the hood?

I don't know - perhaps a air vent/grate embedded in the counter on each side of the stove? Large enough that the air velocity is low.

Posted By GuyB on 13 Aug 2010 08:07 PM
Thanks for the responses. I never stopped to consider NPV.

How would the push-pull configuration introduce the outside air? Down by the countertop on the sides of the cook area or does it need to be distributed accross the hood?

Not everything you do to a home can or should be put through a financial analysis- it's a dwelling, not an investment vehicle, but when you're looking at relatively high-ticket energy efficiency stuff it's not bad to verify that it has at least SOME payoff within the anticipated lifetime of the equipment, and that it has at least as much effect on energy use as some other efficiency measure of comparable or lesser cost that you may have passed up.  In the grand scheme of things all conserved BTUs or kwh in a household energy use patter ARE created equal, but it's always possible to spend ridiculous amounts of money to bring it to the next level.

The low duty-cycle of a residential kitchen and the high up-front cost of a high-flow commercial HRV seems way out of whack, especially if it's a climate where you might want to purge some of that kitchen heat half the year rather than recover it.  Sending 110F kitchen hood air out and returning 105F ventilation/makeup air through an HRV on an 85-90F day isn't exactly the "efficiency" you're looking for.

I'm not convinced there are advantages to push-pull configurations over exhaust-only.  The required makeup air for the burner capacity should be adequate air-inlet for exhaust-venting.  It un-balances the whole-house HRV whenever the kitchen exhaust is running, but that's not usually an efficiency-disaster.

Posted By GuyB on 12 Aug 2010 08:49 PM
Would this work?

I have the plans for a house that goes one step beyond the massive "commercial" stoves that seem to be routinely spec'd in new houses. The cooking area is 9' long and consists of a 36" gas rangetop, 24" elec griddle, 12" fryer, 12" 15k btu wok burner.

There are two 4' hoods over the cook area. The architect specified remote mounted  3 speed 600-900 cfm fan to vent the area and another fan same size interlocked to supply make up air to the A/C system. Since its an A/C only system electric elements are required to heat the air.

I have been looking at commercial HRVs that move the same amount of air. One manufacturer (on the residential side, not sure on the commercial side) suggests exhausting kitchen hood through the HRV if and only if a suitable grease filter is used to capture grease prior to entering the HRV. 

Given that the cost of a commercial HRV of the appropriate size is in the neighborhood of the spec'd system. I would like to get some opinions on whether or not this arrangement would work.

Construction is very tight two story ICF with SIP roof and very careful detailing of all infiltration points.

I've been meaning to respond to this & kept forgetting.  This is really off the topic, but I wanted to at least throw it out there.  With the specs for the kitchen appliances, it seems that the budget is pretty significant.  If that's the case, I'd look for a bigger wok burner.  15,000 btu's really isn't enough to use a wok as it is intended.  Our new range has an 18,000 btu dual flame "power burner" & when larger batches of stir fry, I wish I had more.  I'd go as big as possible with that.

If you're truly going "commercial" with it, one resource may be a restaurant supply store.  Most of the truly commmercial cooking appliances require significant venting because the standards for exhaust gases & such are different in the commercial environment than in a home.  Generally speaking, the commercial appliances are cheaper & work better.  One thing I was warned about at the time I was looking, though, is that some homeowners policies will be voided if commercial appliances are used so that's something to at least look into..