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jeepster
Basic Member
Posts:153
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| 27 Jan 2012 03:30 PM |
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Posted By Liebler on 26 Jan 2012 08:51 PM
I'm planning to exhaust 50 CFM from each bathroom and 50 CFM from the kitchen through a central ERV and distribute the returning fresh air to the bedrooms, family room, living room & dining room. It's my understanding this is code accepted and eliminates individual bathroom fans.
I would worry about doing this. Bath fan size recommendations are 6-8 air changes per hour. If you figure a 10' x 10' bathroom with 9' walls has 900 cubic feet. Multiply this by 8 ACH and you'd have 7200 cu ft of air you need to remove in an hour. Divide 7200 by 60 to figure out what CFM fan you need and it'd be 120 CFM. This is not a large bathroom, yet it's calling for almost 2.5 times what you are planning on installing. Kitchen fans need to be even larger. You are building such a tight house, how will 50 cfm exhaust the smells and humidity from the bath/kitchen. |
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Liebler
Basic Member
Posts:334
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| 27 Jan 2012 08:00 PM |
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I'm basing it on the recommendations for whole house ventilation, but will 'upsize' the whole house system & operate it on a duty cycle to provide the recommended whole house ventilation. When on continuously I'll have 200 CFM total divided between 3 bathrooms and kitchen. The layout of the house has one bathroom next to the kitchen.
The old ASHRAE ventilation recommendation was 0.33 ACH For my dream house comes out to 113CFM
The newer, current ASHRAE ventilation recommendation is 3CFM/100 SQ ft +7.5 CFM/person comes out to only 99 CFM
So I'm well above either. If things get too bad windows and doors could be pressed into service. |
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jeepster
Basic Member
Posts:153
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| 27 Jan 2012 08:58 PM |
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Correct me if I'm wrong, but aren't the ASHRAE ventilation recommendations for continuous ventilation, not including localized ventilation requirements such as bathrooms and kitchens? I'm building a pretty tight ICF house with an ERV, but I elected to install bath fans in each bathroom. A 210 CFM in the master bath, which is about 10' x 16'; a 80 CFM in a half bath (fart fan), which is only 5' x 5'; and a 110 CFM in each of two bathrooms that are about 8' x 10'. The kitchen fan also vents outside. I know this is going against the premise of having a tight house, but tight houses also hold in moisture. |
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Liebler
Basic Member
Posts:334
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| 27 Jan 2012 10:25 PM |
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Jeepster,
You are correct, the ASHRAE recommendations I mentioned are for continuous ventilation. By running a 200 CFM ERV 1/2 the time I'll get an average of 100 CFM as recomended with the capability to have 200 when needed. I believe these recommendations account for the needed moisture removal.
How are you handling the need or make-up air with all that exhaust fan capacity? |
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cmkavala
Veteran Member
Posts:4327
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| 27 Jan 2012 10:32 PM |
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It is not a code requirement to vent the kitchen |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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jeepster
Basic Member
Posts:153
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| 27 Jan 2012 10:56 PM |
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Posted By cmkavala on 27 Jan 2012 10:32 PM
It is not a code requirement to vent the kitchen
Actually, it is a code requirement, but there is an exception listed: M1503.1 General.
Range hoods shall discharge to the outdoors through a single-wall duct. The duct
serving the hood shall have a smooth interior surface, shall be air tight, shall
be equipped with a back-draft damper, and shall be independent of all other exhaust
systems. Ducts serving range hoods shall not terminate in an attic or crawl space
or areas inside the building.
Exception: Where installed in accordance with the manufacturer’s installation
instructions, and where mechanical or natural ventilation is otherwise provided,
listed and labeled ductless range hoods shall not be required to discharge
to the outdoors.
http://publicecodes.citation.com/icod/irc/2012/icod_irc_2012_15_sec003.htm?bu=IC-P-2012-000002&bu2=IC-P-2012-000019 |
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cmkavala
Veteran Member
Posts:4327
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| 27 Jan 2012 11:11 PM |
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Posted By jeepster on 27 Jan 2012 10:56 PM
Posted By cmkavala on 27 Jan 2012 10:32 PM
It is not a code requirement to vent the kitchen
Actually, it is a code requirement, but there is an exception listed:
M1503.1 General.
Range hoods shall discharge to the outdoors through a single-wall duct. The duct
serving the hood shall have a smooth interior surface, shall be air tight, shall
be equipped with a back-draft damper, and shall be independent of all other exhaust
systems. Ducts serving range hoods shall not terminate in an attic or crawl space
or areas inside the building.
Exception: Where installed in accordance with the manufacturer’s installation
instructions, and where mechanical or natural ventilation is otherwise provided,
listed and labeled ductless range hoods shall not be required to discharge
to the outdoors.
http://publicecodes.citation.com/icod/irc/2012/icod_irc_2012_15_sec003.htm?bu=IC-P-2012-000002&bu2=IC-P-2012-000019
There is no requirement to install a hood. The section of the code you are quoting is the requirements IF the hood is installed, however we have built several homes with no hood at all at the request of the owner. One condition of having no hood is that there cannot be anything combustible (wall cabinet) within 30" of the range top |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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jeepster
Basic Member
Posts:153
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| 27 Jan 2012 11:17 PM |
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Posted By Liebler on 27 Jan 2012 10:25 PM
Jeepster,
You are correct, the ASHRAE recommendations I mentioned are for continuous ventilation. By running a 200 CFM ERV 1/2 the time I'll get an average of 100 CFM as recomended with the capability to have 200 when needed. I believe these recommendations account for the needed moisture removal.
How are you handling the need or make-up air with all that exhaust fan capacity?
Haven't really thought about that yet . . . I'm still trying to figure out if my HVAC guys know what they are doing with the ERV. The duct work is roughed in, but no components are in place yet. They basically have an inlet and outlet in the mechanical room. If they are going to plumb it into the return, I'll be curious to see if they place a damper between the fresh air and room air. I'm going to wait and watch, because this will let me know if they have an any idea to what they are doing. |
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Lbear
Veteran Member
Posts:2740
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| 28 Jan 2012 02:20 AM |
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Posted By cmkavala on 27 Jan 2012 11:11 PM
There is no requirement to install a hood.
The section of the code you are quoting is the requirements IF the hood is installed, however we have built several homes with no hood at all at the request of the owner.
One condition of having no hood is that there cannot be anything combustible (wall cabinet) within 30" of the range top
It would depend on the state/county. I know out here in AZ it is mandatory to have a kitchen hood, especially if you are using a gas stove. How else would you vent the by-products of natural gas? |
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cmkavala
Veteran Member
Posts:4327
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| 28 Jan 2012 07:54 AM |
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Posted By Lbear on 28 Jan 2012 02:20 AM
Posted By cmkavala on 27 Jan 2012 11:11 PM
There is no requirement to install a hood.
The section of the code you are quoting is the requirements IF the hood is installed, however we have built several homes with no hood at all at the request of the owner.
One condition of having no hood is that there cannot be anything combustible (wall cabinet) within 30" of the range top
It would depend on the state/county. I know out here in AZ it is mandatory to have a kitchen hood, especially if you are using a gas stove. How else would you vent the by-products of natural gas?
Lbear;
It is not mantatory to have a gas stove either. Most states including Arizona follow the IRC, please tell me the section of the code that states that a hood is mandatory. |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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Bob I
Veteran Member
Posts:1435
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| 28 Jan 2012 02:04 PM |
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RE: Bath vents & poly
I've built several homes without individual bath vents, using the HRV exhaust instead. I've wondered each time if I would get, as has happened in the past with individual exhaust fans, get a call from the homeowner complaining about how long it took to exhaust the moisture. Hasn't happened. I think it probably relates to the fact that the HRV runs continually. I live in an old home without an HRV so have no direct experience, but so far the HRV route seems to be sufficient in the new tight houses. One of my gripes with bath vents is that they seems to be very difficult to air seal so why fight it?
I haven't gotten into the poly discussion, but not convinced that it is necessary to use it in the many applications you're thinking of. If foundation moisture is a concern, you can paint the top of the footing with Drylock; a product that seals out the moisture & prevents it from getting into the foundation wall. That plus a good waterproofing/damproofing on the exterior, plus, of course good (white PVC, not the black corragated junk) foundation drains in stone should keep the moisture at bay.
Bob I |
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| Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant |
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Lbear
Veteran Member
Posts:2740
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| 10 Feb 2012 02:02 AM |
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Posted By cmkavala on 28 Jan 2012 07:54 AM
Lbear;
It is not mantatory to have a gas stove either. Most states including Arizona follow the IRC, please tell me the section of the code that states that a hood is mandatory.
So with an electric range one can get by without installing a hood vent? When cooking onions and other such foods, would the ERV work to remove the smell? |
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ICFHybrid
Veteran Member
Posts:3039
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| 10 Feb 2012 09:21 AM |
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When cooking onions and other such foods, would the ERV work to remove the smell? Yes, because the ventilator exhausts the stale air to the outside along with the odor-causing components being carried by it. How else would you vent the by-products of natural gas? The byproducts of natural gas are CO2, H2O and heat, the same as you produce upon exhalation. |
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Lbear
Veteran Member
Posts:2740
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| 10 Feb 2012 03:54 PM |
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Posted By ICFHybrid on 10 Feb 2012 09:21 AM
The byproducts of natural gas are CO2, H2O and heat, the same as you produce upon exhalation.
When natural
gas is burned, as in cooking and heating, the chemicals create nitrogen
dioxide, carbon monoxide, fine particulates, polycyclicaromatic hydrocarbons,
volatile organic compounds (including formaldehyde) as well as other chemicals.
It is NOT as "clean" as the gas industry claims it to be. Natural gas contains methane
(which gives the flame its blue color as it does in propane), which is an asphyxiate.
People with allergies, asthma and other lung issues tend to have MORE problems in a home that uses natural gas/propane for its stove top cooking.
So venting natural gas has more to do than just with moisture issues, the by products of burnt gas are toxic, albeit in small quantities but still toxic.
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ICFHybrid
Veteran Member
Posts:3039
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| 10 Feb 2012 04:30 PM |
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It's arguable as to what the actual risk is from using gas to cook with as opposed to resistance electric. The exotic chemicals "created" are normally present in extremely small amounts compared to the CO2 and the H2O.
The air exchange created by the whole house ventilation strategies are designed to deal with the real issues (the CO2, H2O and objectionable odors) and as a natural result, the ventilation also deals with the lower level contaminants you want to focus on.
The huge, powerful hoods that you find associated with the commercial style gas ranges are rarely used at full capacity. They have to be big, because the potential heat output, the potential smoke and the potential vapor generation from a powerful range require it. In reality, you don't use it that much. Unless you are a consistently bad cook. I have seen it before. |
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Lbear
Veteran Member
Posts:2740
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| 11 Feb 2012 08:55 PM |
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With my home design, the cooking area was the kitchen island, and we were going to go with an electric grill top. The issue we did not resolve was on HOW to vent the that area due to the tall vaulted ceiling. One option was doing an "in-slab" duct work, which I did NOT like. The other was install a really tall vent hood, which was the better option and the cost was around $1K plus install.
I will have to research more but I will lean towards NO kitchen vent hood OR a really tall stainless steel vent hood. The tall stainless hoods in a vaulted ceiling kitchen look really aesthetically pleasing.
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cmkavala
Veteran Member
Posts:4327
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| 12 Feb 2012 07:39 AM |
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Posted By Lbear on 11 Feb 2012 08:55 PM
With my home design, the cooking area was the kitchen island, and we were going to go with an electric grill top. The issue we did not resolve was on HOW to vent the that area due to the tall vaulted ceiling. One option was doing an "in-slab" duct work, which I did NOT like. The other was install a really tall vent hood, which was the better option and the cost was around $1K plus install.
I will have to research more but I will lean towards NO kitchen vent hood OR a really tall stainless steel vent hood. The tall stainless hoods in a vaulted ceiling kitchen look really aesthetically pleasing.
Lbear;
I have installed under slab ducts befor and I never cared for them either. As long as you have 30" clearance to anything combustible, you really are not required to have a hood, However,if it was me, I would probably still install a wall or ceiling exhaust up high just in case I needed to exhaust smoke from cooking |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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ICFHybrid
Veteran Member
Posts:3039
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| 12 Feb 2012 12:10 PM |
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The downdraft vents present an even bigger challenge for "green" homes. Don't they need to be more powerful than the overhead units in order to capture the same amount of heat, smoke and vapors and force them downwards? That means more noise, more power required and even more air exhausted. Every downdraft vent I have seen in operation has been obtrusively noisy.
I don't really look at my hood as a ventilation device. My motivation stems from fire prevention. Have you ever seen a good grease fire? I'm putting up with the hood, and making it 3" bigger than the range surface on all sides because it provides initial containment for a grease flare-up. |
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Lbear
Veteran Member
Posts:2740
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| 12 Feb 2012 12:17 PM |
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Posted By cmkavala on 12 Feb 2012 07:39 AM
Lbear;
I have installed under slab ducts befor and I never cared for them either.
As long as you have 30" clearance to anything combustible, you really are not required to have a hood,
However,if it was me, I would probably still install a wall or ceiling exhaust up high just in case I needed to exhaust smoke from cooking
Would a furred out steel SIP ceiling hold a stainless steel island hood vent suspended from it? It would be a vaulted T&G ceiling as seen here:  |
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cmkavala
Veteran Member
Posts:4327
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| 12 Feb 2012 09:57 PM |
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Would a furred out steel SIP ceiling hold a stainless steel island hood vent suspended from it? It would be a vaulted T&G ceiling as seen here:
It would depend on weight of hood and thickness/span of panels |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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