There are times when the basement foundation walls already have insulation installed. Wondering if you can frame over it? Luckily, we conducted in-depth research on this matter to help you, and here’s what we discovered.
You can frame over basement insulation but doing so may result in your insulation's resistance of energy flow (R-value) decreasing since the frame may compress the insulation.
In this article, we’ll thoroughly discuss framing and insulations as well as the installation of these. We’ll also share with you the required insulation R-values for basements and the impact of compression. More information ahead so keep on reading.
Can You Frame Over Basement Insulation?
In modern homes, basement insulation is a typical feature. This is the large silver padding that you see tacked to the wall of your basement. However, you might think of what to do with the existing insulation on your basement foundation walls.
It's totally up to you to decide if you are going to remove the current basement insulation and proceed with the proper way of the installation which is framing the walls right up against the foundation. Otherwise, leave the insulation in place and frame over it.
If you did the first one mentioned, you can save space but not much. You will only save around 3” on each side of the room since the insulation puffs out at about 3”. So, the total saving space is 6”.
Moreover, if you decide to tear the insulation down, you need to install it back because insulating the basement is a good idea, of course. This is a little extra work on your end but you can just shred these old insulations and insert them on studs cavities or better buy pre-cut to the proper width of it.
Whereas, framing over the basement insulation and squishing it just to save a few inches of space is a bad idea. Simply because any insulation that has been compressed loses its R-values.
And so, it is no longer a reliable shield against heat and cold. Although the insulation can contact the framed wall studs, don't let them trample it.
What Is The R-Value Insulation For Basement Walls?
The R-Value is one of the important considerations when making plans for the installation of basement insulation. Greater energy efficiency is the outcome of insulation products with higher R-levels.
More warm air is kept inside the house during the winter because less cold air is allowed in from the outside. A greater R-value is necessary for the basement because of its unique characteristics, which include being underground, exposed to groundwater, susceptible to mildew and cold, etc.
With the best basement wall insulation, it will maintain a dry, pleasant, and healthy living environment while saving a homeowner money on heating and cooling.
An acceptable basement wall R-value should prevent thermal bridging, lessen heat loss through the foundation, withstand moisture penetration, guard against damage to the damp-proof coating during backfilling, and lessen condensation on basement surfaces.
The International Energy Conservation Code (IECC) prescribes the R-values for basement insulation according to eight geological climate zones in the United States.
A choice for basements in climate zones 5 through 8 was just added to the 2021 IECC. The modifications enable R-13 insulation inside and R-4 insulation outside. The 2018 IECC allows R-15 insulation on both the interior and exterior and R-19 for interior cavities.
However, the Model Energy Code advises R-11 insulation ratings in most areas and R-15 in the most northern regions for basement walls.
Can Insulation Be Squished?
It’s sometimes difficult to prevent a negative impact on the insulation’s R-value during installation. The R-value per inch increases when you compress batt insulation.
However, the overall insulation R-value decreases since you now have a thinner batt than the one you originally purchased that was tested and rated for a specific thickness.
The amount of loss varies depending on how much insulation is decompressed but normally falls between 15% and 20% of its initial value.
Moreover, if you compress the insulation, you might need to buy more just to meet the R-value needed for your basement which only costs you more.
Simply squishing the insulation will stop it from working and will cause condensation build up as it doesn't have room to breathe. That is why you should avoid squishing the insulation as much as possible to get the most out of it.
But if compressing is unavoidable, it is better to use so-called high-density batts (3 ½” of R-13 or R-15, or 5 ½” of R-21). They are simpler to fluff up, stiffer, and easier to cut around obstructions in wall frames, although costing more than regular batts.
How To Properly Frame And Insulate On The Basement?
Your basement can be as pleasant as any other room in your house by using appropriate framing and insulation techniques.
If your basement wasn't already insulated, you have several options, which is better because you can build it correctly. Below are some detailed procedures to take when performing these tasks.
1. Prepare The Working Area
Examine the basement wall and repair anything that needs fixing. As possible, seal all leakage channels, including those along the sill and surrounding penetrations. This is a vital stage as it offers the fundamental air barrier system.
2. Place House Wrap On The Basement
Putting house wrap on the walls of the basement will prevent any water damage to the frame, insulation, and wall finish.
Plastic was formerly the preferred material, however, condensation might occur in it as moisture and air got into an insulated wall which would then cause wetting and mold issues inside the wall. But through the usage of house wrap, any moisture that seeps through the wall will dry off.
Starting at or just above the grade line, attach the house wrap and insert it into the bottom plate of the frame wall. You may use strapping made of wood (1x3 lumber may suffice) to mechanically support it.
3. Install The Frame Wall
There are two methods you may choose in installing the frame. The first one is constructing the frame wall such that it is near but not touching the house wrap–maybe around ½” space.
The other one involves framing far away from the foundation wall to provide insulation between it. These give the insulation enough room to fit snugly without being compressed.
The second strategy requires more internal space but offers more insulation, better moisture protection, and less thermal bridges between the studs.
Start by installing the bottom plate on a continuous impermeable membrane and the top of the house wrap extension. Next, secure the top plate to the joists' undersides so nailing support is necessary.
Next, space the studs 24" apart, but make sure that this spacing will offer the right amount of structural support for your finishing requirements. The insulation will fit snugly and there won't be any issues with finishing installations if the studs are totally upright and evenly spaced.
If everything is level and square and there are no obstacles, you can fix the wall frame in place. Thereafter, complete any required electrical and plumbing rough-ins.
4. Add Insulation
You can now insert the insulation in a horizontal layer on the gaps between the studs and the foundation wall. After that, add a vertical layer of batt insulation to the frame wall, and fit it tightly between the studs with no gaps but don’t over-compress it.
However, if you are using fiberglass blown-in insulation, use the suggested R-values and densities from the manufacturer to fill all cavities.
5. Place A Vapor Barrier Over The Insulation And Studs For Finishing
If the basement is somewhat dry, a vapor barrier made of polyethylene is appropriate for it. However, there are two different approaches that are more appropriate if you are unsure or there is a chance of moisture in the basement.
Polyamide Sheeting Application
This first approach is a permeable barrier commonly referred to as a smart barrier. This barrier has a water vapor permeance that changes according to the temperature within the wall when installed on the warm side of an exterior wall.
Contrary to typical sheet-type vapor barriers, this smart barrier will dry out toward the interior if the relative humidity on the wall cavity rises.
If you are utilizing a smart barrier, it is still crucial to carefully follow the manufacturer's instructions, especially during the installation process even though its use is comparable to that of polyethylene sheets with a few notable exceptions.
Make sure to allow an extra vapor barrier at the top of the installation so you can attach it to the joist header area. With acoustical sealant, seal all seams, edges, and penetrations.
Then, to seal all joints, run a bead of sealant between the layers of material at the lapping joints where they overlap a stud. Through the sealant bead on the studs, attach the barrier with staples.
Airtight Drywall Technique
This second approach uses both vapor and air barrier systems. Using foam tape and flexible caulk, the drywall is carefully attached to the frame and any other component connections.
To give you a clear visualization of this installation process, a video on YouTube is shown below.
There are other uses for your basement besides utilities and storage. With some forethought and clever tactics, such as good framing and insulation, you can make it efficient. We hope this article clarifies this matter and wish you success with your project.
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