# What would you do?



## McShan (Dec 29, 2017)

We are on the 2012 I codes and 2009 IECC the ac unit is in the attic it is a foam insulated space. The A/C unit's return air is open to the attic space and there is a grill to the living area no duct work connecting them the return air of the unit is pulling air from the space in the attic the only connection to the living space is the grill in the wall 
	

		
			
		

		
	





	

		
			
		

		
	
 the strangest setup I've ever seen.


----------



## fatboy (Dec 29, 2017)

I had trouble following your narrative.

So, basically the entire attic space is a plenum?


----------



## Francis Vineyard (Dec 29, 2017)

Refer to the _approved_ spray foam manufacturer installation guideline such as the ICC ESR and check for compliance. For example may have conditions such as "air in the attic or crawlspace is not circulated to other parts of the building"


----------



## McShan (Dec 29, 2017)

Right i see it as the attic is acting as a plenum.


----------



## cda (Dec 29, 2017)

Not a hvac person 

Another problem

But also pulling bad gases and natural gas off the water heaters???


----------



## cda (Dec 29, 2017)

It is all one envelope ?

House and attic 

Correct?


----------



## cda (Dec 29, 2017)

*Question 4: Will any combustion appliances be located in the attic?*
Once you’ve tightened up your thermal envelope and brought your combustion appliances indoors, you have to come up with a plan to provide your appliance burners with combustion air. The best solution is to install only sealed-combustion appliances in a conditioned attic.

Each sealed-combustion appliance has two big pipes: one is the flue, and the other conveys fresh outdoor air to the burner.

If you hope to convert an existing unconditioned attic to a conditioned attic, the presence of any atmospherically vented appliances (for example, a gas water heater or a gas furnace) complicates the retrofit work. If you can’t afford to buy new sealed-combustion appliances, you’ll probably be better off leaving your attic unconditioned.



Read more: http://www.greenbuildingadvisor.com/blogs/dept/musings/creating-conditioned-attic#ixzz52fdN6Am0 
Follow us: @gbadvisor on Twitter | GreenBuildingAdvisor on Facebook


----------



## cda (Dec 29, 2017)

*Question 5: Is there any need to condition the attic with a forced-air register?*
Okay, you’re coming down the home stretch now. You’ve insulated your sloped roof and your gable walls. You’ve protected any exposed foam with a thermal barrier like drywall. You’ve done your best to limit air leaks in the tricky area at the attic’s perimeter, where the rafters meet the top plates of your exterior walls.

You’ve just created a conditioned attic. Now your HVAC contractor asks you whether or not you want a supply register and a return grille in your attic.

The answer to this question depends on several factors. If you have insulated the roof assembly with closed-cell spray foam, you probably don't need a supply register or return grille in your attic. If you’ve done a good job insulating and air sealing, the temperature of the air in your attic will approximate indoor conditions, even without a supply register or a return-air grille.

If you have insulated the roof assembly with open-cell foam and you live in a humid climate, however, there is increasing evidence that you probably need to install a supply register and a return grille in your attic in order to keep humidity levels low enough to avoid damp roof sheathing. For more information on this issue, see Open-Cell Spray Foam and Damp Roof Sheathing.



Read more: http://www.greenbuildingadvisor.com/blogs/dept/musings/creating-conditioned-attic#ixzz52fdgNSX5 
Follow us: @gbadvisor on Twitter | GreenBuildingAdvisor on Facebook


----------



## Francis Vineyard (Dec 29, 2017)

FWIW technically under the 2012 definition this could be a unfinished storage space or utility room, not be an attic if the door and the return air opening is an adjacent habitable room. The 2015 however change to definition to better define that there can be more than one attic space.

2012 IRC
*ATTIC.* The unfinished space between the ceiling assembly of the top story and the roof assembly.

2015 IRC
*ATTIC.* The unfinished space between the ceiling assembly and the roof assembly.


----------



## McShan (Dec 29, 2017)

No Gas appliances or combustion. The attic is sealed with open cell foam no sheet rock on the rafters completely un-finished. I'm thinking conditioned or semi-conditioned space. My concern if its a plenum all the wire and foam plastic that are not allowed in a plenum. Or is it a condition space just like if they put in a closet in the living area? If this OK, then the supply ducts could be eliminated and just registers opened into each room. Its just odd.


----------



## mtlogcabin (Dec 29, 2017)

A SFD can have any material within a plenum
My concern would be the spray foam insulation and meeting that requirement since there is a specific section that deal with that in attics. I do not believe exception 3 of 602.2.1 would be applicable to spray foam insulation

2012 IMC

602.2.1 Materials within plenums.
Except as required by sections 602.2.1.1 through 602.2.1.5, materials within plenums shall be noncombustible or shall be listed and labeled as having a flame spread index of not more than 25 and a smoke-developed index of not more than 50 when tested in accordance with ASTM E 84 or UL 723.

Exceptions:

1.    Rigid and flexible ducts and connectors shall conform to Section 603.

2.    Duct coverings, linings, tape and connectors shall conform to Sections 603 and 604.

3.    This section shall not apply to materials exposed within plenums in one- and two-family dwellings.

4.    This section shall not apply to smoke detectors.

5.    Combustible materials fully enclosed within one of the following:

5.1.    Continuous noncombustible raceways or enclosures.

5.2.    Approved gypsum board assemblies.

5.3.    Materials listed and labeled for installation within a plenum.

6.    Materials in Group H, Division 5 fabrication areas and the areas above and below the fabrication area that share a common air recirculation path with the fabrication area.


----------



## Rick18071 (Dec 29, 2017)

I only have the 2009 IRC:

Section M1602 Return Air

M1602.2 Prohibited sources:

4. A closet, bathroom, toilet room, kitchen, garage, mechanical room, boiler room, furnace room, unconditioned attic or other dwelling unit.


----------



## fatboy (Dec 29, 2017)

Same in the 2015 IRC.


----------



## cda (Dec 29, 2017)

McShan said:


> No Gas appliances or combustion. The attic is sealed with open cell foam no sheet rock on the rafters completely un-finished. I'm thinking conditioned or semi-conditioned space. My concern if its a plenum all the wire and foam plastic that are not allowed in a plenum. Or is it a condition space just like if they put in a closet in the living area? If this OK, then the supply ducts could be eliminated and just registers opened into each room. Its just odd.





Ok water heaters looked gas fired at first


----------



## Francis Vineyard (Dec 29, 2017)

To further clarify I would review the manufacturer spray foam installation guidelines and contact their technical staff if necessary. This interpretation may provide some insight how the code views a SFP unvented crawl and permits air opening to the living area.

IRC Interpretation No. 48-07


----------



## McShan (Dec 29, 2017)

Thanks for all the input. Its seems like something new every day, as Forrest Gump would say "life is like a box of chocolate your never know what you'll get." The same doing Inspection's. Once again thank you all and have a great new year.


----------



## Builder Bob (Jan 3, 2018)

A typical conditioned attic using a plenum return to keep from having to run duct work...... cheap cheap cheap === to offset cost of spray foam.


----------



## Pcinspector1 (Jan 5, 2018)

Looks like a great space to store my lacquers, leftover paint and Christmas decorations. Plenum or storage room?


----------



## Builder Bob (Jan 5, 2018)

to bad fire codes don't regulate inside your castle..... I agree to a certain degree Pcinspector - however darwinism has to work its magic.


----------



## tmurray (Jan 5, 2018)

If it was my house I'd duct it. Don't think I could make someone else do it though...


----------



## steveray (Jan 5, 2018)

I would have to look alot closer at the foam plastic stuff and separation from the dwelling unit before I would approve it....


----------

