9 Important Benefits of Insulating An Unheated Detached Garage

As an Amazon Associate, I earn from qualifying purchases.

What is the Point of Insulating an Unheated Detached Garage?

Are you planning to build a new detached garage? Just a decent place to park your cars. You want to keep it very basic and simple.  So you have decided not to have any heating. Then what is the point of insulating an unheated detached garage?

Insulating an unheated detached garage takes very little effort. You can do it yourself. It is not too expensive either. Just 5-6% of the total cost of building the garage. Insulation will make your garage more comfortable and increase the life of your cars and other stuff that you may store there.

In this post I will explain all about the ways & costs of finishing a detached garage including the insulation options. You will understand how insulation works and makes your garage a better place not only for you but also for your cars and other precious belongings.

Benefits of Insulating an Unheated Detached Garage

If the garage was heated then insulation would help us reduce energy costs of heating. However, in this case we are saying there is no heating. That is, there is no energy cost. If there is no cost, you can not save!

But without insulation, the garage will get uncomfortable when the outside gets cold.

1. Improving Comfort Level

When it gets cold outside and the temperature drops to 50’s, the temperature in the garage also drops. The temperature in the garage, as compared to the outside temperature, will depend on the combination of heating & insulation in the garage.

As there is no heating, it all depends on the insulation. If there was absolutely no insulation then the outside and inside temperature would be more or less the same.

However, insulating an unheated detached garage could keep the inside temperature 5-20 degrees higher than the outside temperature.

The comfortable temperature range for humans is 70 degrees F. So with really good insulation, we could still be comfortable in the garage, even when the outside temperature is in the 50’s.

2. Prolonging the Life of your Cars

Extreme cold is detrimental to the life and performance of the car. If the temperature in the garage falls below freezing then the cars will be covered in snow and ice, even when parked in the garage. The salt in the deicing chemicals along with water will increase the risk of rust & corrosion.

It is also a lot more difficult to get a car started in the morning when the car has spent the night in a really cold garage.

3. Preventing Damage to Stored Items

Many of the items that you store in your garage are sensitive to extreme temperature. Many items will say “store in a cool, dry place”. So obviously an uninsulated garage is not the place to keep them.

Paint, especially water based paint, can not be stored in a garage, where temperatures can go below freezing. The polymer in cleaning supplies also breaks down in extreme cold.

Household and sports equipment that may have moisture or water, will also deteriorate when the water freezes. Examples are power washers, ceramic flower pots, surfboards, jet skis, canoes, etc.

Musical instruments made out of wood as well as wooden furniture may develop cracks due to contraction in extreme cold. Leather items have similar problems.

4. Increases Garage Structure Life

In addition to protecting stored items, insulation also protects the garage structure from extreme temperature changes. Constant expansion and contraction of building materials due to temperature variations can weaken the structure over time.

Insulation provides stability, enhancing the longevity of the garage.

5. Soundproofing (Noise Reduction)

Insulating material usually absorbs sound very well. So by insulating garage doors & walls you make your garage a quieter place, reducing noise from outside sources such as traffic or neighbors.

The benefits of soundproofing are also desirable if the garage is also used as a workshop, gym, etc. and you do not want to disturb the neighbors.

6. Preventing Ice forming on Garage Floor

Insulation of garage doors & walls helps in reducing humidity & condensation.

In winters, there is a high chance that the snow the car brings in will form a pool of water on the garage floor. If the garage is not well insulated (and that includes insulation of garage walls) then the water on the floor can freeze to ice. This is a safety hazard.

7. Ensuring Water Pipes & Drains do not Freeze

Do you have water pipes & drains running through the garage? In freezing winters, they may freeze and burst if your garage is not well insulated.

8. Property Value Enhancement

A well-insulated garage, even a detached garage, adds to the overall value of your property. Potential buyers are likely to appreciate the added functionality and energy efficiency. As such they will be amenable to paying a somewhat higher price for your home.

9. Reduction in Carbon Footprint

Last but not the least, insulating a detached garage contributes to energy conservation. By reducing your overall energy consumption, you are indirectly helping to lower your carbon footprint and minimize environmental impact.

When do you Really Need Insulation?

The US is a large country with many climatic zones. The weather in Alaska or even upstate New York is vastly different than that in Texas or Florida. 

The International Energy Conservation Code (IECC) has mapped the US counties and assigned an alphanumeric code to each one. The numbers running from 1 to 8 are indicative of the temperature. The alphabets denote the humidity levels. A for Moist, B for Dry and C for Marine.

For example, Sacramento in California is assigned the code 3B because it has a hot, dry climate, while Columbia in Wisconsin is assigned 6A as it has a cold and somewhat moist climate.

Counties with IECC code between 4 and 7 get cold in winters. Detached garages in these counties will certainly be better off with some insulation.

Detached garages in counties with IECC code of 2 or 3 will benefit from insulation too. But they might need a different type of insulation.

Want to know the IECC code for where you live? Check it out from the table on https://gist.github.com/philngo/d3e251040569dba67942

What is Heat Flow & How Insulation Works?

Heat moves from a high temperature area to a low temperature area, just like water flows downhill. It does so by

Conduction

Conduction is the process when heat moves from the high temperature area to the low temperature area through the solid material of the garage wall.

Convection

Convection is the process in which the air in contact with the high temperature area of the garage wall moves and takes the heat away to the colder parts of the garage or to the outside environment.

Radiation

Radiation is the process when the heat moves from the high temperature area to the low temperature area through electromagnetic waves such as visible light, UV rays and infrared rays.

What does an R-Value Mean?

How do you stop the water from flowing downhill? You build a dam.

How do you stop the garage heat from escaping to the cold outdoors? You use insulation. 

Some materials, like fiberglass wool are much better insulators than say steel or a concrete slab. In other words some materials have a higher “resistance to heat flow” than others.

R-Value is a measure of the “resistance to heat flow”. The higher the R-Value, greater is the “resistance to heat flow”. 

Want to know even more? Read my blog post What You Need To Know About R-Value For Garage Insulation.

Note that R-Value applies to “resistance to heat flow” by conduction. In case of heat loss or rather heat gain in climatic zones 2 and 3, a Radiant Barrier is more helpful.

How do you Finish a Detached Garage?

Once the basic shell of the detached garage has been built, you need to finish it to put it to use. Utilities such as electricals & drainage would have already been put in during construction. But what about the walls?

In the US, the most common way of making a wall, especially a garage wall is by making it out of a wooden frame. The frame consists of two horizontal pieces of wood (plates) which are joined by equally spaced vertical pieces of wood (studs).

The wooden frame is finished by using sheathing material on the interior and siding material on the exterior. The stud bays, which is the space between the studs, the sheathing and the siding, can be (and is) used to house utilities, such as cables, conduits, plumbing and insulation.

Sheathing Material

Sheathing of the walls is done by making a wooden frame out of 2X4 or sometimes 2X6 lumber. The frame is made up of vertical studs, spaced 16 inches apart on horizontal top & bottom plates. The frame is attached to the concrete garage floor and sheathing material nailed or screwed on to it.

Drywall is the sheathing of choice for most projects including garages. Low cost, fire resistance and ease of installation make drywall a preferred choice.

However, there are a few good alternatives to drywall too. Plywood & OSB have been gaining acceptance of late.

Stud Bay

Irrespective of what sheathing material you use, you end up creating a cavity between two studs, the wall and the sheathing. This is called a stud bay or just a bay. The bay would be almost 4” deep.

Insulating material can be used to fill the stud bays. It is an opportunity, begging, not to be missed.

Insulation material manufacturers are well aware of this and produce insulation batts or rolls which are 3” to 3 ½” in thickness, for exactly this reason.

Types of Insulation & How Much They Cost?

Insulation for a garage need not be expensive. There are quite a few options available and they are not that costly. Especially when compared to the cost of building a garage.

According to Home Advisor building a garage costs $50 per square foot, on an average. A standard 2 car garage is 20’X20’ (that is 400 square feet).

So a standard 2 car garage is going to cost around $20,000 to build.

Insulating the Detached Garage Walls

The three walls have an area of 3X20’X8’ (that is 480 square feet). Let us see what the insulation material cost (for the 3 walls alone) would be for the different options worth considering.

Insulation Batts or Rolls

Insulation Batts can be made from any insulating material. Typically they use fiberglass but other types of material such as cellulose, mineral wool or natural fibers can also be used.

Standard fiberglass batts have R-Values ranging from R-2.9 to R-3.8 for every inch of thickness. This works out to a R-Value of 9-15 for an insulation batt or roll that is 3” to 3 ½” in thickness. (Perfect for 2X4 stud walls of detached garages).

Owens Corning is pretty much a leader in fiberglass batt insulation. Check out:

Owens Corning R 15 Kraft Faced Fiberglass Batt Fits 2X4 Stud Walls

The above will cost between $1.55 – $1.60 per sq. ft. The material cost of insulation for 3 garage walls works out to $745 – $ 770.

Fiberglass is a skin and lung irritant, so always wear protective eyewear, gloves, masks and clothing when working with fiberglass insulation.

Fire Resistant Rigid Foam Boards

Fire Resistant Rigid Foam Boards are rigid panels usually made out of Expanded Polystyrene (Styrofoam), or mineral wool. The R-Values range from 3.6 to 4.2 per inch of thickness. This works out to a R-Value of 11-15 for an insulation foam board of 3” to 3 ½” in thickness,

ROCKWOOL COMFORTBATT^® is a stone wool insulation product for use in wood and steel framing in both new residential and commercial builds and renovations. This semi-rigid batt has a unique flexible edge designed to compress as the batt is inserted into walls, attics, ceilings and floor frames.

The safety requirements during installation are much lower than fiberglass batts or rolls. R-15 ROCKWOOL ComfortBatt Fire Resistant Stone Wool Insulation from Home Depot costs less than $0.80 per square foot.

The material cost of insulation for 3 garage walls works out to around $375.

Fire Resistance: Please note that both Fiberglass and Mineral Wool are fire resistant and will not burn. However, backing such as paper, foil etc. and the wood studs & joists are not fire resistant and can burn.

Spray Foam Insulation

Spray Foam Insulation is created by injecting two liquid chemicals from a spray gun which react to form a foam. The foam expands rapidly and will fill up every nook & cranny. It then hardens to create a very strong air barrier.

Spray Foam Insulation is extremely energy efficient. However, in my opinion, it is an overkill for a garage wall.

Insulating the Detached Garage Doors

When you buy new garage doors, you always have the option of buying insulated garage doors. However, if you chose to buy uninsulated doors, no worries. It is extremely easy to insulate garage doors & windows using insulation kits.

Expanded Polystyrene Foam Panels

The panels are made of Expanded Polystyrene (EPS) which can significantly reduce heat transfer by conduction. They often have a decorative and functional lamination of High Impact Polystyrene (HIPS) facer that adds both beauty & strength.

The lamination could also be reflective to reduce heat transmission through radiation. It is a great idea to buy the “Bundle”, costing around $175 – $200, as under:

Garage Door Insulation Kit (Bundle)

The cost for a 2 door garage will work out to $350 – $400 for this option.

Fiberglass Wool Panels

The panels are a lot more flexible and are made by sandwiching fiberglass insulation wool within a tough, washable white vinyl facing on both sides. They do not dent due to the flexible nature.

Owens Corning Garage Door Insulation Kit

The kit costs around #$175. The installation is quite simple and very little DIY expertise & experience is required in both cases.

Insulating the Detached Garage Ceiling

You can lose a lot of heat through the garage ceiling during night and cooler months. So insulating the ceiling is pretty important. The recommendation is to go for at least R-38 insulation in climate zone 4.

Garage ceilings can be sheathed in plywood or drywall and can be insulated using

Insulation Batts or Rolls

This is similar to wall insulation, except that you need much higher thickness to get to the required R-Value. Owens Corning has just the product for attic application.

Owens Corning R-38 Unfaced 24 by 48 Fiberglass Batt Fits 2X12 attic

This product will cost a little over $2 per sq. ft. The material cost of insulation for 400 square foot garage ceiling works out to around $800 – $825.

The installation is quite simple and very little DIY expertise & experience is required.

Blown-In or Spray Foam Insulation

Blown-in or spray foam insulation are other options, but they require the use of contractors or specialists and are not the cost effective choice for Insulating an Unheated Detached Garage.

Insulating the Detached Garage Floor

Generally speaking, insulating the garage floor is a good idea especially for really cold climates. However, since you have chosen to keep the detached garage as basic as possible and are even skipping on heating, I will not recommend this.

Insulating the garage floor can be expensive. But should you want to learn more about it check out my earlier blog post How To Insulate Your Garage Floor And Save More!

How Much Does Insulating an Unheated Detached Garage Cost?

In summary, the total material cost of insulating a standard 2 car, 20’X20’ garage will be:

AREA	MATERIAL COST
Three Walls	$745 – $ 770
Two Doors	$350 – $400
Ceiling	$800 – $825
Floor	NA
TOTAL	$1895 – $1995

The material cost of insulating a unheated detached garage represents less than 10% of the cost for building a garage.

Bottom Line

The bottom line is that insulating even an unheated detached garage can make it better by making it more livable and prolonging the life of your car and other precious belongings. It does not cost much and you can do it yourself.

So why not?

Thank you very much for reading the post. I do hope you found it informative and useful.