Is insulation required between garage and house?

Author: Waldo Hills  |  Last update: Tuesday, January 13, 2026

Creating a robust air barrier between a garage and living spaces isn't just a plus; it's also required by the International Residential Code (IRC). The most straightforward way to achieve this separation with an attached garage is to first frame, sheathe, and air-seal the house, then frame and sheathe the garage.

Should I insulate between garage and house?

You should definitely insulate. Regardless of weather you have to, you will want to. Garages are pretty much considered exterior, any they get pretty hot/cold, especially if they aren't finished. You don't want that temperature fluctuation messing with your interior temps. Insulate for sure.

Do you need a vapor barrier between garage and house?

The majority seem to agree that insulated, unheated garages, should be allowed to breathe. If the garage is heated, you will need a vapor barrier, otherwise you will get frost and mold.

How do you insulate a garage wall between your house?

If the garage has a cavity wall construction, then this can typically be insulated with blown insulation such as polystyrene balls. If the cavity is too slim for this, or if there is no cavity (a solid wall), then the only options are to fit external wall insulation (EWI) or internal wall insulation (IWI).

What kind of wall goes between garage and house?

People commonly misuse the word firewall to refer to the wall between the garage and the house. The wall between the house and garage is actually called a fire separation wall, not a firewall. A firewall is a fire-resistance-rated wall. It extends from foundation to or through the roof.

Should I Insulate the Wall Between the Garage and House? | Foam University

What is the space between garage and house called?

A breezeway is an architectural feature similar to a hallway that allows the passage of a breeze between structures to accommodate high winds, allow aeration, or provide aesthetic design variation.

Is a firewall required between garage and house?

Conclusion. In short, the garage needs to be separated from the house in case of fire, but this isn't a fire-rated assembly, nor is it a firewall. The best term for this required separation is a fire-separation wall.

Do you put insulation between walls?

In many cases, condensation occurs inside the shared wall between rooms. Insulating these walls separates the different air temperatures, slows heat transfer, and reduces the risk of moisture problems that can lead to mold or mildew.

Can you insulate garage walls without removing drywall?

A blowing machine is needed to properly install cellulose insulation as it aerates it. Due to its insulation structure, cellulose can only be used in finished garage walls or attics. However, if drywall is already in place, the cellulose can still be installed by cutting holes between studs and blowing it in.

What is the U value for a wall between a garage and a house?

Insulation in Garage Conversions

Existing walls need to achieve a U-value of 0.3, existing roofs a U-value of 0.16 and the existing floors should achieve a u-value of at least 0.25. Any new walls or floors require a U-value of 0.18 and new roofs a U-value of 0.15.

Should I use faced or unfaced insulation in my garage?

Faced insulation is also a good idea if you are putting in first time insulation. Perhaps you've liked the warmth and energy protection of an installed insulated garage door and want even more insulation. If you're already adding insulation over existing insulation, faced insulation isn't necessary or suggested.

Is Tyvek a vapor barrier?

Is DuPont Tyvek® a vapor barrier? No, DuPont Tyvek® is not a vapor barrier. It is made with unique material science to keep air and bulk water out while allowing moisture vapor inside walls to escape.

Should I put plastic over insulation before drywall?

Should I Put Vapor Barrier Plastic Over Insulation Before Drywall? Yes, covering your insulation with a vapor barrier plastic before installing drywall is crucial. It prevents moisture buildup that can lead to mold, rot, and even structural damage.

Why no insulation over garage?

Instead of Insulating the Garage Attic

It isn't important to insulate the ceiling between the attic and the garage because those areas are not affected by a home's heating and cooling system. It is important to insulate any walls that separate the garage from air-conditioned rooms in the house.

How much does it cost to insulate a 24x24 garage?

The cost to insulate a 24' x 24' garage is $3,000 - $8,000. Garage size influences the cost of insulation. The 24'x24' garage will house 2 cars and some extra space for other purposes. The average cost to insulate a 24x24' garage with spray foam is $6,000.

Do I need a vapor barrier when insulating my garage?

Homes in areas with high humidity and occasional temperature drops will also experience garage condensation. Combining a vapor barrier with Comfortbatt® insulation will further improve moisture control in the space as it's water and moisture resistant. It does not absorb moisture to maintain its insulating value.

Should wall between garage and house be insulated?

In the same way, if the wall between the house and garage isn't insulated properly, the entire envelope of the home won't be sealed up. This means the rooms adjacent to the garage will experience air loss and drafts -- one of the main reasons you wanted to re-insulate the walls in the first place.

Does it make sense to insulate an unheated garage?

Attached garage insulation can reduce the cost to heat or cool your home. Creates more comfortable living spaces. An insulated garage makes it easier to control the comfort in adjacent spaces.

What is the cheapest way to insulate a garage wall?

The cheapest way to insulate an unfinished garage is with fiberglass batts or rolls for $0.80 to $2.60 per square foot installed.

Why do builders not insulate interior walls?

Interior walls are often left uninsulated during construction because the energy efficiency benefits are less significant than those gained from insulating exterior walls, floors and ceilings.

What is the cheapest way to insulate internal walls?

Thermal lining paper is among the cheapest ways to insulate internal walls. This thick, insulating wallpaper can be easily applied directly to walls, making it a quick and straightforward solution. Costing around £10 per square metre, it effectively reduces heat loss and is perfect for smaller DIY projects.

How do I know if my walls need insulation?

Cold Walls, Floors and Ceilings

The interior ceilings, walls and floors in your home should feel warm and dry. When drywall and paneling inside a home feels damp or cold, there is not enough insulation.

What is the building code for a door between garage and house?

The IRC requires the door between the house and the attached garage to be a minimum of 1 3/8 inches thick – either a solid wood door, a solid or honeycomb-core steel door, or a 20-minute fire door.

What insulation for a garage?

We recommend using fiberglass insulation, since this type is easier to handle and can be used throughout the entire garage, including the walls, floors and ceiling. If you plan to use a different type of insulation, we suggest hiring a professional, since other materials can require more experience.

Is it worth having a firewall at home?

Firewall protection at home is generally considered smart and worthwhile, as it adds a critical layer of security to your home network.

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