Insulate garage ceiling

shorthairsrus

Founding Member
Founding Member
Joined
Apr 13, 2015
Posts
8,422
Likes
486
Points
383
So my ceiling has 5/8 (or whatever is standard for ceilings) sheetrock --- but no insulation. i pretty sure its 2x4s (late 90s home). So what can i put up for insulation. I was thinking about blowing it in --- but then i read that my ceiling may not be able to take the weight. The roof is vented and i was carefully going to put a couple soffitt vents in.

Ideas?
 


LBrandt

★★★★★ Legendary Member
Joined
Apr 3, 2016
Posts
10,831
Likes
1,384
Points
498
Location
SE ND
If its trussed rafters there aint noway in hell that blowing insulation is going to cause a weight problem. Just stop at recomened R-factor.
 

DirtyMike

Founding Member
Founding Member
Joined
Apr 13, 2015
Posts
12,063
Likes
360
Points
418
Location
Bismarck, ND
Yep, blow in insulation is your ticket. Really isn't all that bad if you have someone feeding the blower. Just be sure not to load it up on top of your soffit. I just cut a piece of plywood to fit between the rafters to deflect any over spray.
 

Ruttin

Founding Member
Founding Member
Joined
Apr 21, 2015
Posts
1,308
Likes
639
Points
293
Location
ND
Blow-in and make sure you have adequate venting. Also installing the sytro foam insulation chutes between the rafters is a must.
 
Last edited:


Obi-Wan

Founding Member
Founding Member
Joined
May 15, 2015
Posts
7,496
Likes
2,525
Points
678
Location
Bismarck
You will need more than a couple vents on the eave

Guidelines for attic ventilationNew building code requirements may limit roof system designsby Mark S. GrahamProper attic ventilation can be an important performance consideration when designing and installing steep-slope roof systems.Typically, building codes include minimumrequirements applicable to attic ventilation.The roofing industry also has practical guidelines for attic ventilation.Code requirementsThe International Building Code,® 2012Edition (IBC 2012) requires enclosed atticsand enclosed rafter spaces formed whereceilings are applied directly to the undersideof roof framing to have cross-ventilation foreach separate space. The net free vent area(NFVA) shall not be less than 1:150 of thearea of the space being vented. Blocking andbridging must be arranged so they do notinterfere with air movement; air space noless than 1 inch must be provided betweenany insulation or obstruction and the roofsheathing. Ventilation openings must be protected to prevent rain or snow infiltration.An exception to IBC 2012’s ventilationrequirement permits the NFVA to be reducedto no less than 1:300 as long as 50 to 80percent of the ventilating area is provided ator near the upper portion of the space beingvented or where a vapor retarder is providedon the warm-in-winter side of the ventilationspace.The International Residential Code,® 2012Edition (IRC 2012) contains requirementssimilar to IBC 2012 except IRC 2012 limitsthe net free ventilation reduction from 1:150to 1:300 when at least 40 percent but nomore than 50 percent of the required ventilation area is provided at or near the upperportion of the space being ventilated.Also, when using a vapor retarder in an atticspace, IRC 2012 limits the net free ventilationreduction from 1:150 to 1:300 for buildingsin Climate Zones 6, 7 and 8.NRCA guidelinesRegarding attic ventilation,NRCA recommends designersprovide at least 1 square foot ofNFVA for every 150 square feetof attic space (1:150 ventilationratio) measured at the attic floorlevel (ceiling). For large-volumeattics, such as where roof slopesare greater than 8:12, designersalso should consider increasingthe amount of attic ventilationto account for the additionalvolume of attic space.Furthermore, NRCA also recommends the amount of ventilation in static ventilation systemsbe balanced, as shown in thefigure, between the soffits or eaves and theupper portion of the space being ventilated.In a balanced ventilation configuration,ambient outside air enters into the attic spacevia soffit or eave vents; this air passes throughthe attic space where it displaces warm,moisture-laden air, which, in turn, exits theattic via vents at or near the top of the spacebeing vented. This configuration relies onconvection—a mode of heat transfer thatcauses warm air and water vapor to rise.NRCA considers use of the balanced ventilation approach to be an important designconsideration for proper attic ventilation performance. It needs to be recognized it is notreadily possible to vent more warm, moist airout of an attic than the amount of new airallowed into the attic, such as with soffit oreave vents.In unbalanced attic ventilation situationswhere the NFVA at or near the top of thespace being vented greatly exceeds that of thesoffit or eave vents (such as is permitted inIBC 2012), it is possible for a slight negativepressure to be created in the attic space. Thishas the potential to allow conditioned airfrom the occupied areas below the attic to bedrawn into the attic. Unsealed openings inthe ceiling plain, such as ceiling recessed lightfixtures, exhaust fan openings and plumbingvent stacks, are common areas of conditionedair loss into attics.Additional information about attic ventilation is provided in the Condensation andAir Leakage Control Section of The NRCARoofing Manual: Architectural Metal Flashing,Condensation and Air Leakage Control, andReroofing—2014. 123MARK S. GRAHAM is NRCA’s associate executive director of technical services.
 

shorthairsrus

Founding Member
Founding Member
Thread starter
Joined
Apr 13, 2015
Posts
8,422
Likes
486
Points
383
It has ceiling vents and i am assuming the entire eave is open to air--- i thought i would have my kid push down some eave vent thingys down a fair number of them if not all.

- - - Updated - - -

ceiling -- roof vents is what i meant

- - - Updated - - -

thingys = chutes
 

Kurtr

Founding Member
Founding Member
Joined
Apr 12, 2015
Posts
18,240
Likes
1,973
Points
648
Location
Mobridge,Sd
Staple the styrofoam vents every other rafter that go to the soffit. Blow in required amount of insulation. There is a roof vent so you are good to go.

F6F2E898-9087-494D-A19D-930E30F0CB14.jpeg
 

Taylorman55

Founding Member
Founding Member
Joined
Jul 15, 2015
Posts
640
Likes
83
Points
200
Location
Hazen ND
Staple the styrofoam vents every other rafter that go to the soffit. Blow in required amount of insulation. There is a roof vent so you are good to go.

56ABB7FC-B63B-4179-AA11-2478700E7C19.jpg

^ This. We just did dad's new shop ceiling. Put one of those every other rafter and blew in insulation. One guy up in the rafter running hose and other guy feeding the machine. Did a 40x40 in about 2.5-3 hours of getting after it, came out to R80+ (was shooting for r70-75 but we overshot a bit). Absolutely zero issues with the extra weight.
 


Bfishn

Founding Member
Founding Member
Joined
Dec 7, 2015
Posts
3,849
Likes
251
Points
333
I believe if you buy the insulation at Menards you get to use the machine for free. I did my garage about 7-8 years ago so my mind is a little fuzzy but i think that was the deal. One guy feeding the machine, one guy up top blowing...easy peasy. The Styrofoam vent things were already installed in my garage attic as well so i just let her rip, just make sure not to clog them.
 
Last edited:

Zogman

Founding Member
Founding Member
Joined
Apr 20, 2015
Posts
4,487
Likes
1,558
Points
528
Location
NW Angle, MN and Grand Forks, ND
Wouldn't you need a vapor barrier (clear plastic) between the sheet rock and the new blown in insulation??? And why not put the chutes between every rafter???
 


Kurtr

Founding Member
Founding Member
Joined
Apr 12, 2015
Posts
18,240
Likes
1,973
Points
648
Location
Mobridge,Sd
Wouldn't you need a vapor barrier (clear plastic) between the sheet rock and the new blown in insulation??? And why not put the chutes between every rafter???

No vapor barrier and every rafter is a waste of money
 

Zogman

Founding Member
Founding Member
Joined
Apr 20, 2015
Posts
4,487
Likes
1,558
Points
528
Location
NW Angle, MN and Grand Forks, ND
Would you not use vapor barrier with metal ceiling? Most recent new construction I have seen are using white metal for ceiling and with the new LED lighting you could perform surgery in there.
 

Motor Mouse

Founding Member
Founding Member
Joined
May 15, 2015
Posts
103
Likes
10
Points
113
i think the original question may have been in regards to the 5/8 inch sheetrock and the weight it can carry without sagging a few years later or worse tearing loose and dropping! is the rock nailed or screwed and how often? 24" inch spacing on the rafters. Google the subject .... more info you want! You can go with either fiberglass or cellulose blow in. Both have advantages and disadvantages. In your case fiberglass might be the better choice as it will be lighter. Another advantage is it does not settle like cellulose. But cellulose has some advantages over glass. Sheetrock is rated on the load it can carry. It is easy to find that info as well as weight per square foot for a given R value for both insulation types.

i agree with Kurtr...no vapor barrier on the ceilings! But air tight on the walls. Depending on your construction you will have to use the styrofoam baffles between each rafter to block the blow in insulation from getting into your soffit area. They are cheap and staple in place.
area.
 

tikkalover

Founding Member
Founding Member
Joined
May 10, 2015
Posts
7,940
Likes
902
Points
473
Location
Minot
When I was a roofer 32 years ago we called them "proper vents" now they are called " attic rafter vent baffles".

The 1970 something house I live in now, I bought 26 years ago, had 6"s of fiberglass insulation in it. First thing I did was blow another 15 to 18 inches of blow in insulation on top of that. Haven't had any ceiling issues yet.
 


Recent Posts

Friends of NDA

Top Posters of the Month

  • This month: 160
  • This month: 136
  • This month: 120
  • This month: 110
  • This month: 105
  • This month: 87
  • This month: 84
  • This month: 79
  • This month: 76
  • This month: 76
Top Bottom