The reality is that most post and beam homes have poor or no insulation, especially ones that were built more than 30 years ago. The most important part of house insulation is in the roof – that’s why new construction standards now require 60-R roof insulation.
The cost of adding ceiling insulation to a post and beam home is $4-7.5 per square foot, includes labor and materials.
Your total cost will depend on the type of insulation you use. Material prices can range from as little as a $1.0 per square foot to as much as $5.00 per square foot.
However, due to framing design limitations, you will be lucky to have any sort of outdated cold roof insulation. Most commonly though, your house will not be insulated at all!
Insulating an exposed beam ceiling
Such is the case with my house (picture above) – it is a 1958 custom-built A-frame with 6×12″ timbers and 2×6 tongue and groove roof boards. Inside you see the boards and shingles are on the outside. No insulation at all.
As a result, even with relatively low natural gas prices, the heating bill during last year’s coldest month was over $450 for a 1600 sq.ft. house, of which 500 sq. ft. is a newer, well insulated addition. Pair an un-insulated roof with hollow 2×4 stud walls and tons of large single pane picture windows, and you get a perfectly UN-INSULATED house.
So, having an eco-conscious mindset, I decided to insulate my home. First, I wanted to see if Mass Save would provide any energy efficiency grants or credits.
However – my house construction makes it eligible ONLY for blown in insulation in vertical walls, of which I have very few. My biggest heat loss comes from the roof, which does not qualify for retrofit application, and single pane glass windows, which Mass Save does not have any credits for.
So after my energy audit, it became clear that I will have to pay for pretty much everything out-of-pocket.
At the same time, my entire remodeling project is on hold, until I insulate the roof – before I do it, I cannot replace floors, paint or replace the kitchen.
Retrofit Insulation Types For A Post and Beam Home
People who build or buy post and beam homes, usually get them for the natural wood looks. Thus, insulating these houses from the inside defeats the purpose of having such an architectural style in the first place.
Here are the best insulation types you can use, without sacrificing the look you love.
1)Rigid Board PolyISO roofing insulation with wood strapping – This is my choice!
I chose this option for several reasons:
1. It is the least expensive and most efficient way to install an adequate amount of insulation in your roof, and it is a completely DIY friendly choice.
2. No need to install 2×6 rafters, eliminating unnecessary framing work and the risk of damaging the roof (when nailing 2×6 rafters to the roof / ceiling boards).
3. Relatively easy to do, even for an occasional DIY homeowner, who is willing to put in the work (or hire a handyman and direct the project).
Watch this video, which explains insulation options for Post and Beam open ceilings and benefits of installing PolyISO roofing insulation from inside the house:
2) Insulate From The Inside – Add Fiberglass or Spray Foam Insulation Between Rafters
This second option is great if your goal is to have MORE insulation. You can solve the issue of concealing exposed wood boards by installing Tongue and Groove boards over 2×6 rafters.
You can add nearly 20-R of fiberglass insulation between the rafters, or if you are feeling adventurous and have lots of cash – hire a spray foam insulation contractor.
By installing a Closed Cell Spray Foam between the rafters, you can add 36-R of insulation (6-R per 1 inch thickness). Note that Spray Foam insulation is a CONTRACTOR only option, as it requires special equipment and supplies are available only to specialized professionals.
You can buy Spray Foam kits to do it yourself, but you are paying $1 per 1 square foot, at 1″ cured thickness. So to add 5″ of insulation (30 R-value) you will pay $5 / square foot.
Using Roofing PolyISO insulation you get the same results at $1.75 per square foot (insulation cost only) which is 1/3 the price!
CONS of installing Fiberglass/Spray foam insulation between rafters:
1. Costly and time-consuming framing job – adding rafters between the beams and trying to PROPERLY attach the rafters to Roof Boards.
2. Low R-value in case of using fiberglass insulation or blown in fiber insulation.
3. High cost and a huge mess of installing Spray Foam Insulation.
4. Also – spray foam is NOT a Do It Yourself project, so you have to hire a contractor to do it.
3) Add Roof Insulation From The Outside
My first option was to add Nail Bas insulation on the roof side, when I replace my old asphalt shingles with a new Standing Seam Metal Roof – a project I plan to do next year.
I was going to live one winter with no insulation, and then add 2-3 inches of PolyISO roofing insulation with laminated OSB sheets on top of the existing roof deck. Then I could screw my metal panels into OSB.
However this approach is prone to leaks IF you cannot cover the roof before it rains. Because stripping old shingles and adding insulation panels is very time-consuming, this project would have to be done in small sections and would take over a month to complete, making costs very high, and insulating properties very low (12-18 R).
This would be a decent option for a new construction project, but for me it was not a good solution.
PROS of insulating from outside:
- Preserve the original look of Post and Beam Homes on the inside.
- No need to install Tongue & Groove boards or Drywall
- Does not disturb your living space
CONS of insulating from outside:
- Costs more, because you need to replace your roof, which adds about $5800 (cost of new asphalt roof, based on 1590 sq. ft. average US roof size).
- Creates risks of roof leaks during installation
- Increases cost / inch of Insulation thickness (R-Value) by about 75-100%
- Requires raising the ROOF profile and installing ALL NEW trim boards, which further increases costs
Costs of adding retrofit insulation to existing Post and Beam homes
Let’s look at how much the above 3 options will cost – prices below are for MATERIALS only.
Option 1) Installing 4×8′ sheets of PolyISO Rigid Foam Insulation Boards with strapping.
Cost per foot for insulation – $0.32 per square foot for 1 inch thickness (6-r). In my case I use 5 inches (30-R) of PolyISO so my cost per foot is $1.60 per square foot.
Additionally, I use roofing 7″ screws ($220 for a box of 1000) and double 1×3 strapping (about $250 for whole house).
My total cost for 1120 sq. ft. of insulation is $2,248 or a grand total of $2.01 per square foot (materials only, before tax).
Option 2) Adding Nail Base insulation to the exterior part of the roof:
This can only be performed by a roofing contractor (unless you also do roofing), and requires roof replacement. If your roof is fairly new and you don’t plan to replace it any time soon – this option IS NOT for you.
Cost: $3.50-10 per sq. ft. for new roof and $3-4/sq. ft. of new ISO insulation with laminated OSB boards.
Option 3) This is very time-consuming, and will be especially complicated, if you have high ceilings.
Framing out 2×6 rafters: $1-1.50/ft for materials.
Fiberglass insulation: $2-3 / ft.
Closed Cell Spray Foam: $7-8 per foot (5.5″ – 33-R) to hire insulation contractor.
Buying your own spray foam kits will cost about $1 per 1 sq. ft. coverage of 1″ cured thickness – so to get 5.5″ you will pay $5.50/sq. ft. for DIY spray foam kits.
DIY Installation of Post & Beam Ceiling Insulation
Watch this 12 minute video (original footage was over 30 minutes), which shows how I did it:
