# Minimum window size - NOT egress issue, but based on "room size" - is this an IRC requirement?



## KarlaE (Aug 25, 2021)

My plans are in plan review; several items were just redlined including the size of the windows in two rooms - note from plan review states "window shall be 8% of total room size" - is this actually in the code?  Both windows are 34" x 48"; the one in the bedroom is casement style and meets egress requirements.  One room is 11' 9" x 17' 5" and the other is 13' 4" x 17' 5".

I am building a 50' x 60' metal building with living quarters inside (meets local zoning); the living quarters run the entire 50' length and are 17' 5" wide.  All windows are on the north side of the building, as the south wall is common to the shop area.

Local jurisdiction uses IRC as the standard for plan review - I'm trying to determine if this "8% rule" is legitimate.  My steel building is in production with the window openings given above; the draftsman who drew my plans was very knowledgeable and mentioned window size for egress purposes, but said nothing about this?  Can anyone provide feedback regarding this?  Thanks!


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## cda (Aug 25, 2021)

Welcome 

Not my area, give it a few days

You can go directly to the plan reviewer,,,, and ask nicely for the code sections,,, so you can review them,,,

And post here

Wonder if it has to do with ventilation??? First  I heard that one.,

Any state or local amendments to the code???


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## steveray (Aug 25, 2021)

There are exceptions but....

R303.1 Habitable rooms. Habitable rooms shall have an
aggregate glazing area of not less than 8 percent of the floor
area of such rooms. Natural ventilation shall be through windows,
skylights, doors, louvers or other approved openings to
the outdoor air. Such openings shall be provided with ready
access or shall otherwise be readily controllable by the building
occupants. The openable area to the outdoors shall be not
less than 4 percent of the floor area being ventilated.
Exceptions:
1. The glazed areas need not be openable where the
opening is not required by Section R310 and a
whole-house mechanical ventilation system is
installed in accordance with Section M1507.
2. The glazed areas need not be installed in rooms
where Exception 1 is satisfied and artificial light is
provided that is capable of producing an average


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## cda (Aug 25, 2021)

8% of separation rule!!!!

Sounds like increase window size???

See more of the great state of Nevada


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## cda (Aug 25, 2021)

Building Code Of The Day 12/09/2018 Wenatchee Home Inspections | NCW Home Inspections, LLC
					

Habitable room ventilation and glazing requirements per 2015 IRC



					www.ncwhomeinspections.com
				











						How to Calculate Natural Light and Ventilation? | Explained! – Building Code Trainer
					






					buildingcodetrainer.com


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## KarlaE (Aug 25, 2021)

steveray said:


> There are exceptions but....
> 
> R303.1 Habitable rooms. Habitable rooms shall have an
> aggregate glazing area of not less than 8 percent of the floor
> ...


THANK YOU!  I am installing a 3 ton HVAC system and there are ceiling fans in each room - not to mention the LIGHTING - your post seems cut off at the end  - "capable of producing an average...." I will review Section R310 but it seems that my build meets the parameters of Exception 1...  

In one of the rooms I have a closet that runs the entire width (17') of the room - is that floorspace excluded from this requirement?  If so, that may be an option in the other room - add a long closet!


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## KarlaE (Aug 25, 2021)

cda said:


> Welcome
> 
> Not my area, give it a few days
> 
> ...


Thank you for the warm welcome - I certainly will be spending much time here.  The fellow in charge of the local building department does NOT like owner/builders - so he finds ways to antagonize them.  I have a friend that did a similar build two years ago - I called him to ask if there were such requirements for his build and he said "no".


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## KarlaE (Aug 25, 2021)

KarlaE said:


> THANK YOU!  I am installing a 3 ton HVAC system and there are ceiling fans in each room - not to mention the LIGHTING - your post seems cut off at the end  - "capable of producing an average...." I will review Section R310 but it seems that my build meets the parameters of Exception 1...
> 
> In one of the rooms I have a closet that runs the entire width (17') of the room - is that floorspace excluded from this requirement?  If so, that may be an option in the other room - add a long closet!


CLOSETS!!! (can't have too many)   The IRC defines a *Habitable Space* as _“A space in a building for living, sleeping, eating or cooking. Bathrooms, toilet rooms, closets, halls, storage or utility spaces and similar areas are not considered habitable spaces.”_


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## cda (Aug 25, 2021)

KarlaE said:


> Thank you for the warm welcome - I certainly will be spending much time here.  The fellow in charge of the local building department does NOT like owner/builders - so he finds ways to antagonize them.  I have a friend that did a similar build two years ago - I called him to ask if there were such requirements for his build and he said "no".


Check agsinst your adopted code book::;



*R303.1 Habitable Rooms*

Habitable rooms shall have an aggregate glazing area of not less than 8 percent of the floor area of such rooms. Natural _ventilation_ shall be through windows, skylights, doors, louvers or other _approved_ openings to the outdoor air. Such openings shall be provided with ready access or shall otherwise be readily controllable by the building occupants. The openable area to the outdoors shall be not less than 4 percent of the floor area being ventilated. 

Exceptions:

The glazed areas need not be openable where the opening is not required by Section R310 and a whole-house mechanical _ventilation_ system is installed in accordance with Section M1507.
The glazed areas need not be installed in rooms where Exception 1 is satisfied and artificial light is provided that is capable of producing an average illumination of 6 footcandles (65 lux) over the area of the room at a height of 30 inches (762 mm) above the floor level.
Use of sunroom and patio covers, as defined in Section R202, shall be permitted for natural _ventilation_ if in excess of 40 percent of the exterior sunroom walls are open, or are enclosed only by insect screening.


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## cda (Aug 25, 2021)

Plus read the definitions 


*WHOLE-HOUSE MECHANICAL VENTILATION SYSTEM. *An exhaust system, supply system, or combination thereof that is designed to mechanically exchange indoor air for outdoor air where operating continuously or through a programmed intermittent schedule to satisfy the whole-house ventilation rate

Not sure a normal home hvac system meets this ??


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## KarlaE (Aug 25, 2021)

cda said:


> Check agsinst your adopted code book::;
> 
> 
> 
> ...


I'm reading that right now... next will be to contact the HVAC contractor to see if I do/can meet Exception 1; then to call Electrical contractor to add lighting to meet Exception 2 - and all closets if all else fails!


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## e hilton (Aug 25, 2021)

KarlaE said:


> but it seems that my build meets the parameters of Exception 1...


I think the purpose of exception 1 is that the windows do not have to open. Doesnt say anything about an exception frommthe 8% requirement.


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## cda (Aug 25, 2021)

KarlaE said:


> I'm reading that right now... next will be to contact the HVAC contractor to see if I do/can meet Exception 1; then to call Electrical contractor to add lighting to meet Exception 2 - and all closets if all else fails!




You may just not want to do the exception, especially in Nevada:::




			https://www.homeinnovation.com/~/media/Files/Reports/TechNote_WH_Ventilation_10252013.pdf
		


You will be sucking Death Valley in!!!!


Up size the windows!!!


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## Sifu (Aug 25, 2021)

Glazing can be eliminated if adequate mechanical ventilation and artificial light is provided.


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## Min&Max (Aug 25, 2021)

I agree with Sifu. By referencing the exceptions you can eliminate the need for windows. And if the dwelling is sprinkled even egress windows may be open for debate.


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## KarlaE (Aug 25, 2021)

e hilton said:


> I think the purpose of exception 1 is that the windows do not have to open. Doesnt say anything about an exception frommthe 8% requirement.


I think that it does, as it goes on to say that "if you meet the mechanical requirements for ventilation AND the lumens output" (lighting) - then the 8% does not apply


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## KarlaE (Aug 25, 2021)

cda said:


> You may just not want to do the exception, especially in Nevada:::
> 
> 
> 
> ...


The framed openings in my STEEL building are under construction; I have also RECEIVED my windows - very expensive to make changes now.  I can swap the location of the "bedroom" to the "exercise room" (which is exempt from the rule) - that will meet the glazing requirements for one room.  The "kitchen" is a point to ponder......


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## cda (Aug 25, 2021)

Min&Max said:


> I agree with Sifu. By referencing the exceptions you can eliminate the need for windows. And if the dwelling is sprinkled even egress windows may be open for debate.



Ye but

Doesn’t call for “”” Whole House””.

Isn’t that a little different than normal air conditioning system??????


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## KarlaE (Aug 25, 2021)

KarlaE said:


> The framed openings in my STEEL building are under construction; I have also RECEIVED my windows - very expensive to make changes now.  I can swap the location of the "bedroom" to the "exercise room" (which is exempt from the rule) - that will meet the glazing requirements for one room.  The "kitchen" is a point to ponder......


possibly remove 50% of the wall to open it to the other room with all the light....have an "open floorplan"


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## KarlaE (Aug 25, 2021)

Min&Max said:


> I agree with Sifu. By referencing the exceptions you can eliminate the need for windows. And if the dwelling is sprinkled even egress windows may be open for debate.


No sprinklers.... going for ventilation & artificial lighting.... though I might reduce the size of the partition wall by 50% to go the "shared lighting" avenue - I like an open floorplan


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## mp25 (Aug 25, 2021)

As long as egress window is present in the bedroom, then the rest can be satisfied with artificial light and mech. ventilation. Easiest way to do whole house mech vent is to have one of the bath exhausts run 24/7 or a specific ratio - to provide the minimum required air volume per unit of time.


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## Rick18071 (Aug 26, 2021)

Getting off track a little but I wonder what the code says about existing houses where the basement or garage was turned to habitable space with no or less then 8% window openings with no other ventilation, just baseboard heaters installed, but the rest of the house does have a whole -house ventilation system? Does the code require windows or ventilation to be added?


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## e hilton (Aug 26, 2021)

KarlaE said:


> I think that it does, as it goes on to say that "if you meet the mechanical requirements for ventilation AND the lumens output" (lighting) - then the 8% does not apply


Ok, looks like you are right, with the caveat that you have to meet exception 1 before exception 2 is available.


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## steveray (Aug 26, 2021)

Rick18071 said:


> Getting off track a little but I wonder what the code says about existing houses where the basement or garage was turned to habitable space with no or less then 8% window openings with no other ventilation, just baseboard heaters installed, but the rest of the house does have a whole -house ventilation system? Does the code require windows or ventilation to be added?


We verify that when they pull a permit to finish it....With typ basement windows and a door/ hatch, it usually works....But the door is key


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## KarlaE (Aug 26, 2021)

mp25 said:


> As long as egress window is present in the bedroom, then the rest can be satisfied with artificial light and mech. ventilation. Easiest way to do whole house mech vent is to have one of the bath exhausts run 24/7 or a specific ratio - to provide the minimum required air volume per unit of time.


That seems that path of least resistance....and I only have one bath exhaust...and it is at the far end of the living quarters, so running it 24/7 will not bring a "noise issue" - I will research what volume/rate will comply with the Mechanical Code mentioned previously in this thread so that I can purchase a fan to meet these requirements.

Ditto for the artificial lighting... I'll put in additional recessed lighting in the ceiling divided across several individual switches so that the lighting is there, but not all come on at the same time (I don't like a lot of light)

Thanks for your suggestion!


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## Min&Max (Aug 26, 2021)

cda said:


> Ye but
> 
> Doesn’t call for “”” Whole House””.
> 
> Isn’t that a little different than normal air conditioning system??????


In my opinion exceptions 1 & 2 in R303.1 of the 2018 IRC make it possible to build a dwelling without any windows whatsoever. Again in my opinion, M1505.1 through M1505.4.1 resolve all ventilation issues relating to windows. I think the homeowner has enough info that the AHJ should strongly reconsider their original determination.


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## steveray (Aug 26, 2021)

Min&Max said:


> In my opinion exceptions 1 & 2 in R303.1 of the 2018 IRC make it possible to build a dwelling without any windows whatsoever. Again in my opinion, M1505.1 through M1505.4.1 resolve all ventilation issues relating to windows. I think the homeowner has enough info that the AHJ should strongly reconsider their original determination.


For ventilation you mean...EERO still applies...


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## ICE (Aug 26, 2021)

If 8% is the threshold and the threshold has not been met, what percentage is proposed?  That whole house fan idea is a poor idea.  You do realize that you will have to undercut the doors and/or provide pass through grills into the other rooms?  What about the electrical use for a fan that runs forever?....and the noise?


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## ICE (Aug 26, 2021)

I did the math....you missed by a mile.


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## cda (Aug 26, 2021)

ICE said:


> If 8% is the threshold and the threshold has not been met, what percentage is proposed?  That whole house fan idea is a poor idea.  You do realize that you will have to undercut the doors and/or provide pass through grills into the other rooms?  What about the electrical use for a fan that runs forever?....and the noise?




Someone got the hint!!!

Plus will be pulling Death Valley Air in!!!


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## KarlaE (Aug 26, 2021)

cda said:


> Someone got the hint!!!
> 
> Plus will be pulling Death Valley Air in!!!


There are no doors on either room - just openings in the wall - the "house" is only 925 SF - the two rooms in question are next to each other... electrical will be negligible - I'm calling my HVAC person today


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## cda (Aug 26, 2021)

KarlaE said:


> There are no doors on either room - just openings in the wall - the "house" is only 925 SF - the two rooms in question are next to each other... electrical will be negligible - I'm calling my HVAC person today



Has the city blessed your alternate plan??


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## Min&Max (Aug 26, 2021)

mp25 said:


> As long as egress window is present in the bedroom, then the rest can be satisfied with artificial light and mech. ventilation. Easiest way to do whole house mech vent is to have one of the bath exhausts run 24/7 or a specific ratio - to provide the minimum required air volume per unit of time.


I do not believe it has to run continuously per M1505


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## KarlaE (Aug 26, 2021)

cda said:


> Has the city blessed your alternate plan??


I have not approached them with it yet... I want to thoroughly review the requirement of the mechanical/artificial lighting so that I can overcome any objections that they may have... I want a checkmate!  My metal building won't be erected until the end of October...then the build pertaining to this issue starts, so I have a bit of time.  I will certainly post the results....


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## e hilton (Aug 26, 2021)

ICE said:


> I did the math....you missed by a mile.


Can you expound a little please.


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## Sifu (Aug 26, 2021)

Whole house ventilation is defined in the commentary:
"an exhaust system, supply system or combination thereof that is designed to mechanically exchange indoor air for outdoor air.  The system can either operate continuously or it can be programmed to operate intermittently."

So if an air handler has an outdoor air intake and the whole house is served by this air then you have "whole house ventilation".  The IRC mandates the outdoor air based on the size and number of bedrooms.  So if a system is being installed in compliance with the code it is permissible to have less than the 8%.


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## KarlaE (Aug 26, 2021)

Sifu said:


> Whole house ventilation is defined in the commentary:
> "an exhaust system, supply system or combination thereof that is designed to mechanically exchange indoor air for outdoor air.  The system can either operate continuously or it can be programmed to operate intermittently."
> 
> So if an air handler has an outdoor air intake and the whole house is served by this air then you have "whole house ventilation".  The IRC mandates the outdoor air based on the size and number of bedrooms.  So if a system is being installed in compliance with the code it is permissible to have less than the 8%.


That's what I thought - there will be a 3 ton unit to service 925 SF


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## Paul Sweet (Aug 26, 2021)

3 tons sounds high for 925 SF unless you have a lot of southwest facing glass, or your insulation is way below IECC standards.


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## KarlaE (Aug 26, 2021)

Paul Sweet said:


> 3 tons sounds high for 925 SF unless you have a lot of southwest facing glass, or your insulation is way below IECC standards.


NO southwest facing glass - insulation in 2 x 6" studs INSIDE a metal building with 6" insulation all the way around - which bodes well for this unit handling the "ventilation issue" and allowing me the exception - speaking with the HVAC contractor in the morning - I have already introduced the idea of the exemption to the building official and asked "do you accept this"? He said that he did... I need to put my numbers on paper for him.


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## KarlaE (Aug 26, 2021)

Sifu said:


> Whole house ventilation is defined in the commentary:
> "an exhaust system, supply system or combination thereof that is designed to mechanically exchange indoor air for outdoor air.  The system can either operate continuously or it can be programmed to operate intermittently."
> 
> So if an air handler has an outdoor air intake and the whole house is served by this air then you have "whole house ventilation".  The IRC mandates the outdoor air based on the size and number of bedrooms.  So if a system is being installed in compliance with the code it is permissible to have less than the 8%.


I agree - reading this page confirms your suspicions - and I am installing a 3 ton HVAC system; now I need to calculate the lights needed to meet the lighting requirement and I'm golden...


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## KarlaE (Aug 26, 2021)

KarlaE said:


> I agree - reading this page confirms your suspicions - and I am installing a 3 ton HVAC system; now I need to calculate the lights needed to meet the lighting requirement and I'm golden...








						Whole-House Ventilation Strategies | Smarter House
					






					smarterhouse.org


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## steveray (Aug 27, 2021)

An oversized HVAC system is never the answer....I think you only get 15-20% oversizing on the cooling side per manual S...40% on heating...


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