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Should I insulate the ceiling of my garage

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The walls in my garage were insulated when the house was built, 2009, the ceiling was not. It's a 3 car garage, ranch style house and it gets below freezing in the winter and very hot in the summer in the garage.

The garage is unheated and I store our boat in the 3rd stall. I used to like working in the garage in our old house, split entry, garage under the bedrooms and water didn't freeze in that garage. We live in eastern Nebraska where the winters can be very cold for weeks at a time. If I insulate the garage do I put soffit vent baffles in between all the rafters?
asked in Car Garage by tabboud (120 points)
edited by darekrudy
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1 Answer

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Hi Tabboud,

I apologize for a delay in getting you this answer, busy Monday smiley.
I’m missing some information about your garage; 
  1. Does it have a drywall finished ceiling and no insulation on top of the drywall / attic shared with the rest of your house’s attic?
  2. Is the garage’s ceiling open, only framed with no surface finishing material, space open to the house’s attic?
  3. Are you planning to condition the garage; install a heating and / or cooling unit? Un-conditioned garages rarely have insulated ceilings and exterior walls.
Insulating the garage’s ceiling without conditioning of this enclosed space may not give you that many benefits. It might keep it slightly cooler in the summer and maybe a few degrees warmer during the cold season but if the high or freezing temperatures persist for a few days the benefit of that temperature differential is mostly from the fact that the garage’s interior is shaded by the roof and protected with walls and doors from wind and other weather conditions.
So, if you already have drywall installed on the ceiling and you’re not planning to use any heaters / AC in the garage, adding insulation on the ceiling will probably not change much. Just make sure there’s a good air flow, sufficient amount of ventilation in your attic.
If you have no drywall on the garage’s ceiling and this space is open into the attic directly above the living area, than you should finish the ceiling with drywall to create required firewall separation. Another solution is to extend the common wall between the house and the garage all the way to the roof and maintain an open ceiling for the garage area. You can check this link - garage firewall
Using baffles in between the rafters isn’t necessary at all; it all depends on the type of insulation used and skills of the installer. Properly installed batt insulation where there’s sufficient space left for the air to travel from the soffit into the attic doesn’t require baffles.
You can also use short pieces of batt insulation for areas along the soffit and fill the rest of the ceiling with blown-in type insulation. It’s all explained in my article - http://checkthishouse.com/3913/attic-vent-chutes-does-your-attic-ventilation-require-any.html
Let me know if you have more questions, just click “comment” below.
answered by darekrudy (21,730 points)
The ceiling is drywalled and the attic is shared with the rest of the house. There is no insulation over the garage but the rest of the shared attic is covered with blown in insulation.Perhaps in the coldest months I could use a space heater if I wanted to work in the garage, would insulating the ceiling help with a space heater?
If you are planning on using a space heater than the insulation will help to keep the heat inside the garage. However, don't expect miracles unless you have a very powerful space heater and insulated or solid wood overhead doors.