# Combustion Air



## conarb (Nov 28, 2010)

With these new envelope sealing codes why isn't combustion air being required for gas appliances?  I've installed a lot of large hotel/restaurant style ranges, even a 48" to 60" Viking has 8 burners and requires 1480 cfm exhaust ventilation, that's a lot of makeup air.



			
				Viking said:
			
		

> CFM stands for Cubic Feet moved per Minute. Generally, it is recommended  that for every 100 BTUs of heat generated by a cooking vessel, the  blower in a hood should move 1 CFM of air.¹


 ¹ http://www.vikingrange.com/consumer/products/category_products.jsp?id=cat10005#category-product-info-support


----------



## Francis Vineyard (Nov 28, 2010)

Assuming we are discussing residential codes will it be covered in the gas code section for combustion, ventilation and dilution air?

It seems that most if not all of the gas appliances will require to be direct vented and blower door test will ultimately require a HRV or ERV or some other fresh air device.

Energy conservation suffers the law of unintended consequences.


----------



## conarb (Nov 28, 2010)

Addressing a gas range, especially a large commercial type in a residence, my understanding is that RG2447.2 bars commercial gas appliances in residential usage; however, California's new residential code does not adopt those portions, instead defaulting to the UMC and UPC.  We can install hotel/restaurant type equipment in residence, and companies like Wolf and Viking make 48" to 60" gas ranges that are approved for residential for both us and the rest of the nation, but ranges that require 1,480 cfm exhaust ventilation. Many in the cold portions of the country as well as the hot.humid areas are hermetically sealing their buildings, which begs the question as to where the 1,480 cfm for a Wolf or Viking range is going to come from.  This also assumes that they are going to have to install other gas appliances like furnaces and water heaters outside the conditioned envelope, otherwise why seal the minuscule air leaks up and allow huge openings for combustion air?  But, gas ranges can't be installed outside the envelope.

I am unfamiliar with ERVs and HRVs, do they allow air to come in?  They must, as I understand their function they bring in outside air and condition it but attempt to recapture energy from air being exhausted, so they must still be a pipeline to the exterior like the combustion air to furnaces and water heaters. In California we must now provide 0.35 ACH continuous ventilation from the exterior, to pass AQ testing in homes built with engineered lumber we are having to crank the 0.35 up to 1.0 or even 3.0, much like situation with the sick commercial building syndrome of the 80s. This totally negates any benefit of the envelope sealing so highly touted by the energy efficiency mavens and the fan industry.


----------



## Sandman (Nov 28, 2010)

http://www.vikingrange.com/MEDIA_CustomProductCatalog/m1750052_F20470.pdf

See page 2 under the Important, Please Read and Follow heading, "Check with a qualified and trained installer or local codes for makeup air requirement, if any."

M1503.4: “Exhaust hood systems capable of exhausting in excess of 400 cfm shall be provided with makeup air at a rate approximately equal to the exhaust air rate. Such makeup air systems shall be equipped with a means of closure and shall be automatically controlled to start and operate simultaneously with the exhaust system.”


----------



## conarb (Nov 28, 2010)

Sandman:

I have never seen makeup air installed in a kitchen to serve a hood. If one were to install makeup air, how would it only become available when the hood is running at a specific speed?  If the makeup air is always available for the highest usage necessary what's the point of sealing homes up for energy efficiency?


----------



## Sandman (Nov 28, 2010)

Make up air can be introduced in any number of locations in the kitchen, soffits, under toe kicks, behind the refrigerator, through the ceiling, etc. In cold climates in-line duct heaters might be necessary to condition the air. A relay switch from the exhaust hood to the motorized damper in the make up air duct will act as the control and multiple settings might be necessary depending on exhaust fan speeds.

People that can afford these high end cook tops can afford the additional work to prevent depressurization and backdrafting.

Introducing outside air through the forced air system might be an alternative solution and avoid the in-line heater but sizing and damper controls would present a problem.


----------



## Dr. J (Nov 29, 2010)

M1503.4: “Exhaust hood systems capable of exhausting in excess of 400 cfm shall be provided with makeup air at a rate approximately equal to the exhaust air rate. Such makeup air systems shall be equipped with a means of closure and shall be automatically controlled to start and operate simultaneously with the exhaust system.”

Conarb:



> I have never seen a code compliant large kitchen hood.


There - fixed it for you.



> If one were to install makeup air, how would it only become available when the hood is running at a specific speed? If the makeup air is always available for the highest usage necessary what's the point of sealing homes up for energy efficiency?


If the air is going up the hood, it IS coming into the building, by backdrafting through flues if the building is tight enought.  In a leaky buiding from the good ole days, it would come in all the time.   By providing make up air in a tight building (preferably with a HRV)  energy is used to condition OA only when needed.  If the hood is multi speed, the make up air unit needs to be also.


----------



## conarb (Nov 29, 2010)

> by backdrafting through flues if the building is tight enought.


   But my good doctor, won't it come though the combustion air supplies at both the water heaters and furnaces?  What about through the bath fans?  California's new Energy Code requires continuous (or on a time clock) whole house ventilation, won't it draft thorough there?


----------



## Dr. J (Nov 29, 2010)

Yep, sure will.  Thus the code requirement to provide a "planned" path for make-up air for large kitchen hoods.


----------



## conarb (Nov 29, 2010)

Dr. J. said:
			
		

> Yep, sure will. Thus the code requirement to provide a "planned" path for make-up air for large kitchen hoods.


  Can you quote chapter and verse on that? How many of our inspectors enforce that? I've never done anything like that, and no inspector has ever checked for it, these new tight houses are a whole new world.  I don't see how they are tight anyway, no-matter how tight you build them there are, and always will be, combustion air vents, bath fans, and now whole house fans.  I think the hermetically sealed home is a pipe dream.


----------



## Dr. J (Nov 29, 2010)

See previous posts (M1503.4).


----------



## Sandman (Nov 29, 2010)

From our good friend Joe Lstiburek, "All buildings require controlled mechanical ventilation. Building intentionally leaky buildings and installing operable windows does not provide sufficient fresh air in a consistent manner. Building envelopes must be 'built tight and then ventilated right.' Why? Because before you can control air you must enclose it."

Builder's Guide to Cold Climates, Details for Design and Construction, Lstiburek, J., Taunton Press. Newton, CT 2000


----------



## Mac (Nov 30, 2010)

Conarb, how many of these hotel/restaurant style ranges have you installed?

Have any of those installations experienced a ventilation-related problem?

Doc has the chapter & verse, and we can always defer to the mfr's specs.


----------



## conarb (Nov 30, 2010)

Mac said:
			
		

> Conarb, how many of these hotel/restaurant style ranges have you installed?


 I've only built one home with a true commercial kitchen, that was 30 years ago the owner supplied the appliances that came from a hotel and restaurant supply, that home wasn't sealed up, a modern home with acres of aluminum framed single pane glass windows, it had a huge side-by-side glass doored refrigerator, a huge fan that I helped move up on the roof, and two kitchen commercial dishwashers.  I've installed maybe a dozen large Wolf and Viking "commercial style" ranges that were undoubtedly rated for residential use, the last one had a 2,500 cfm fan mounted remotely on the roof, it is only used on the low setting because it sounds like a jet airplane taking off if you turn it up, but none of my homes have been sealed up like the Lstiburek crowed is pushing.



> Have any of those installations experienced a ventilation-related problem?


None to my knowledge, this subject came up from the Lstiburek-Holladay crowd, the save-the-earth-it's-coming-to-an-end, tax-carbon-output-and-give-it-to-the-developing-world crowd pushing green building and zero energy homes. These guys are a bunch of nuts (Lstiburek is in it for the money but is their guru) but never underestimate the influence they have, look at our green and energy codes now. This is the influence coming from the aging Hippie crowd, they are basically anti-war socialistic egalitarians, many are actually Gaians, it really bugs me that we are incorporating their religion into our codes.  They are not only a religion they are a political party, the Green Party has a lot of power in Europe, and we have a city here with a mayor from the Green Party.We ought to fight these things, but I fear it's too late, enforcing these codes is tantamount to enforcing political and religious dogma. Making people sick in sealed-up homes is one of the consequences of ill-thought-out codes.


----------



## Sandman (Nov 30, 2010)

ConArb vs. the ICC, DOE, ASHRAE, WBDG, GSA, DoD (yes, the military employs energy efficient building practices), IRS (energy efficient home credit) and modern science. The code people addressed your concerns regarding the high CFM exhaust fans, but because you have not seen the code enforced, you cannot accept this as true.

When you cannot articulate an intelligent argument, try to convince your audience that "the aging Hippie crowd, anti-war socialistic egalitarians" are behind all of this.

Some of us are making a very good living from these wars.


----------



## conarb (Nov 30, 2010)

Sandman:

I probably work in the area of the country with the most stringent engineering and code enforcement, I've posted this link before to a home with 7 straight days of framing inspection, repeatedly questioning the structural engineering and demanding that it be redone, not one thing was even looked at relevant to makeup air for the large kitchen range. If in fact our homes are getting sealed up to the extent discussed in the Green Building Adviser, inspectors should start looking at makeup air. Personally I think adequate air is entering around window seals, combustion air to water heaters, combustion air to furnaces, bath fans, and our new requirement for whole house fans, but the issue has been raised. I don't think there is, or there is going to be, a problem, but they do, I think the bigger problem with sealed up homes is the formaldehyde and other toxic gasses in engineered wood products and plastics incorporated in many new homes.  Sealed-up homes are a huge problem besides rotting out in a few years, they are toxic and I think the whole combustion air thing to ranges is a red herring.



			
				Examiner said:
			
		

> Initially, we could not understand why homes in Los Altos were  different from homes in nearby communities. Construction practices and  construction materials should be similar throughout the county. The difference was a green building ordinance passed by the City of  Los Altos in late 2007. Beginning in January 2008, all new homes in Los  Altos were required meet the criteria for GreenPoint Rated.
> 
> To be GreenPoint rated, a home has to meet energy conservation  requirements. Those requirements mean that new Los Altos homes are more  tightly sealed than homes in other cities.¹


Green and energy conservation should be personal choices dictated by one's religious and political beliefs, not part of our building codes, but for now they are causing huge problems with unintended consequences.

¹ http://www.examiner.com/environmental-health-in-san-jose/elevated-formaldehyde-new-los-altos-homes


----------



## Sandman (Nov 30, 2010)

I agree with you on the issues of indoor air quality but these issues have already been addressed.  We acknowledge that tighter buildings lower the air change and that this creates a potential for increases in interior pollutants (from people, moisture, soil, formaldehyde, VOCs from carpet, paint & adhesives, radon, and carbon dioxide (burning of oil, coal & gas). Tobacco smoke is still one the biggest contributors to indoor air pollution yet people still smoke inside right next to their kids.

To mitigate the effects of interior air pollution in tight buildings and to provide a safe and healthy indoor environment, less toxic material selections and adequate provisions for outside air and ventilation (balanced system) must be made. Manufacturer’s have recognized the need for more low emission building materials and sealed combustion equipment choices and like everything else, we will see these prices go down as demand goes up.

If the minimum requirements of Sections 4-7 of ASHRAE 62.1-2004, are met, the work is code compliant, the occupants don’t smoke, and low-emitting materials are used, we can all expect to live long and productive lives as long as we are not poisoning ourselves with other voluntary lifestyle choices (abusive drinking, drugs, unprotected sex, overeating and high-fat diet, chronic stress, sedentary lifestyle and lack of exercise, to name only a few). Since heart disease remains the leading cause of death in the USA, I would be more concerned with the voluntary lifestyle choices than I would with the ppm of formaldehyde in my kitchen cabinets.


----------



## conarb (Dec 1, 2010)

Let's get back to Combustion Air, "building scientists" in the Northeast talk about "sealed-combustion appliances", I asked my mechanical contractor about them and he says there is really no such thing, that inspectors here are still requiring combustion air to gas fueled appliances, does anyone have any information on "sealed-combustion appliances"? Maybe the difference is that we are still on the 2007 UMC (even with the 2010 codes), and not the IMC?


----------



## Sandman (Dec 1, 2010)

Let Google be your friend.

"Sealed Combustion Appliances" will yield about 57,200 results.

Sealed Combustion Appliances are heating appliances (water or air) that vent directly to the outdoors. They do not require air from the inside of the building like combustion appliances. This mitigates the hazard from backdrafting (spillage) of harmful gasses into the building from depressurization.

Water heater combustion air supplied directly to water heater from exterior via duct; products of combustion exhausted directly to exterior also via duct. The ductwork is usually PVC and is very quick and clean to install.

AO Smith makes a good power/direct vent water heater and I have had success with the installation of several hundred Rheem Power Vented water heaters in LEED certified military housing.

http://www.hotwater.com/lit/im/res_gas/185884-001.pdf

Furnace flue gases exhausted to the exterior using a fan; combustion air supplied directly to furnace from exterior via duct. Most high-efficiency furnaces are designed as sealed combustion systems, and are well suited to energy efficient tight construction.


----------



## conarb (Dec 1, 2010)

I checked the UMC:



			
				2007 UMC said:
			
		

> 701.1.1 Air for combustion, ventilation, and dilution of flue gases for gas utilization equipment installed in buildings shall be obtained by application of one of the methods covered in Sections 701.2 through 701.8.3. Gas "utilization equipment of other than natural draft and Category I vented appliances shall beprovided with combustion, ventilation, and dilution air in accordance with the equipment manufacturer's instructions. Where infiltration does not provide the necessary air, outdoor air shall be introduced in accordance with methods covered in Sections 701.4 through 701.8.3.
> 
> Exceptions:
> 
> ...


It appears to say that if the manufacturer does not require makeup air that it is not required (other than gas dryers), I wonder why inspectors are making my mechanical contractor install it anyway?


----------



## Sandman (Dec 1, 2010)

Can't answer that.

But, I have always preferred IAPMO over ICC when it comes to plumbing & mechanical.  For water heaters, see also 2009 UPC Section 510.2.5. The commentary I have from IAPMO on this section reads, "The venting system of a direct-vent appliance is considered to be part of its listing. Listed appliances are tested with inlet and outlet configurations taken from their installation directions. Therefore, the installation instructions must be followed carefully."


----------



## Dr. J (Dec 1, 2010)

> Exceptions1) This provision shall not apply to directvent appliances.


Direct vent is another word for sealed combustion.  The inspectors should not be requiring additional holes in the building.

As to why - cynical response is because that is the way they have always done it.

However, a direct vent/sealed combustion boiler/furnace/water heater is completely different from the OP subject of needing make up air for a large kitchen hood.  What it does influence about the OP is that in a properly consructed building, designed and installed to minimize infiltration, and with direct vent heating appliances, there is minimal/no means for providing air to a large kitchen hood exhaust without a specific make up air unit.


----------



## JBI (Dec 1, 2010)

And the manufacturers require make up air for almost all appliances...


----------



## conarb (Dec 1, 2010)

Do we don't need combustion air for water heaters and furnaces if they are "sealed-combustion appliances", but we do need it for gas dryers and gas ranges, is that a fair summary?


----------



## JBI (Dec 1, 2010)

Sealed combustion units provide their own combustion air through the intake. Most solid fuel appliances have air intake ports for combustion air. Many 'gas log' type appliances have air intake ports. Why not stoves?


----------



## Sandman (Dec 2, 2010)

ConArb,

Since 2005  I have  enjoyed these discussions with you no matter where I was or what identity I assumed at the time.  There were a few times when I enjoyed just rattling your cage a bit. In a few days I have to go back to 60-84 hour work weeks in Iraq and/or Afghanistan so my participation in this forum will end again.  Below is my tutorial on Combustion Air and Makeup Air.

Combustion Air

Gas ranges and gas dryers would require additional combustion air if the volume of space in which the appliance is installed is LESS than 50 cubic feet per 1000 Btu/h of the aggregate input rating of the equipment (definition of a CONFINED space).

In most situations, the volume of space in which the appliance is installed in addition to rooms communicating with that space  is greater than 50 cubic feet per 1000 Btu/hr (definition of UNCONFINED space, IRC M1702.2, UMC 701.2.1).

For example, a homeowner wants a Viking model DGCU155-6B, 45-inch, 6 burner gas ceramic cook top installed in her kitchen. The kitchen is 15' x 15' with 10' ceilings (2250 cu.ft.) and  opens to a  dining room 10' x 15' with 10' ceilings (1500 cu.ft) and a living room 18' x 14' with 10' ceilings (2520 cu.ft.). Total volume of space = 6270 cu.ft.

The manufacturer specifications with the burners set to high for this model are

12,000 BTU , 8,000 BTU , 10,000 BTU ,14,000 BTU ,8,000 BTU ,6,000 BTU for a total aggregate input of 58,000 Btu/hr. 58,000 Total Btu/hr/1000 x 50 = 2900 min. cu.ft. required. So, 2900 cu ft is required for combustion air and 6270 cu. ft is provided. There is sufficient air for combustion for this appliance in this space. If a gas range is present in the same space, then the aggregate input of that appliance must be added to the cook top and must be less than 6270 cu.ft.

In a building of ORDINARY TIGHTNESS, all combustion air may be from inside the space and adjacent spaces. In a building of UNUSUALLY TIGHT CONSTRUCTION defined by the IRC as having plastic film vapor retarders with a rating of 1 perm or less with all openings gasketed or sealed,  heavy caulking and sealing around all window and door frames, between sole plates and floors, between wall-ceiling joints, between wall panels and at all penetrations with less than 0.5 air changes per hour, combustion air must be provided for from the outside. The only residential construction that I have been involved with that  came close to meeting this definition was in Alaska.

Makeup Air

M1503.4 (new to the 2009 code): “Exhaust hood systems capable of exhausting in excess of 400 cfm shall be provided with makeup air at a rate approximately equal to the exhaust air rate. Such makeup air systems shall be equipped with a means of closure and shall be automatically controlled to start and operate simultaneously with the exhaust system.”

Since the cook top must be ventilated, the homeowner wants a Viking 48" Wide Chimney Wall Hood - VCWH, model VCWH4848. The VCWH4848 requires 1200 cfm in 10-inch duct with a max. run of 50 feet. Since 1200 cfm exceeds 400 cfm per M1503.4, makeup air must be provided by gravity or mechanical means or both. To comply with the code, one way is to wire the wall hood ventilator motor, model DEV1200, to a motorized damper in the 10-inch makeup air duct (to be approximately equal with the exhaust).  The motorized damper must operate simultaneously and at the same speeds as the wall hood ventilator. The makeup air ductwork can come into the space anywhere convenient, soffits, ceilings or high in an exterior wall.

 So, the wall hood ventilator removes cooking odors and moisture generated by the cook top at a rate of 1200 cfm and the makeup air duct work replaces the air removed at a rate of about 1200 cfm (since the wall hood ventilator creates a slight negative pressure, makeup air is permitted to be equal or  slightly less than the amount of the exhaust air). This action only occurs when the wall hood ventilator is switched on. In a typical household, I  would suspect these motors would be operating less than two hours a day.


----------



## Dr. J (Dec 2, 2010)

Excellent post Sandman.  One picky item:



> Since the cook top must be ventilated


I do not believe there is any requirement for the cooktop to be ventilated, so the better statement would be "Since the design includes ventilation for the cooktop...".  The requirement for make up air is dictated because the owner CHOSE to have a hood over 400 cfm.

I bet a lot of people neglect to consider the volume of the space a gas range is installed in.  Although most kitchen layouts should have sufficient volume, particularly since many floor plans are open to the kitchen, a large range in a small "pantry kitchen" could be an issue.


----------



## conarb (Dec 2, 2010)

Fantastic post Sandman, probably the best answer to a question ever on this or the former ICC Bulletin Board.  Have a good time in your 60-84 hour work weeks in Iraq and/or Afghanistan !


----------



## Daddy-0- (Dec 3, 2010)

I have enjoyed reading this thread even though it is slightly over my head. Thanks for all of the great answers and debate. I have a feeling that this type of problem is only the beginning with some of this energy stuff.

Sandman. Keep your head down and stay safe. I will miss your participation in this forum.


----------



## Jobsaver (Dec 3, 2010)

Same as Daddy-O. Great questions, great answers, though over my head sometimes. Thanks for the effort. Protection and blessing and safe return to Sandman at war!


----------



## peach (Dec 4, 2010)

You can bring fresh air directly into the return air duct.  You've never seen a house with a fireplace and suckmaster 5000 range hood running, have you?  The house goes negative in a hurry.


----------

