Basement Floor Insulation: Key Facts

The basement area represents roughly 20% of the total heat loss in a house. If you want to renovate your basement, it's best to insulate the basement floor first, not only to improve your overall comfort but also to save on your heating and cooling bills. Are you in the middle of building a new home? Or are you simply renovating your home and looking to insulate your basement floor? Keep reading to learn more about it!

What Does it Mean to Insulate a Basement Floor?

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Basement floor insulation consists of top-layer insulation. In other words, the insulation is laid on top of your basement floor, thus making it accessible and fit for use as a living space. For greater thermal comfort, you can also insulate the other surfaces in your basement, i.e. your walls or ceiling. Note that this work can be done either during a construction or a renovation project.

Is Insulating Your Basement Floor Worth It?

When attempting to address the issue of energy loss in the home, like heat loss, basement and floor insulation normally figures at the bottom of any priority list. In other words, we tend to focus on the attic, windows, and doors. However, basement floor insulation is a key factor when it comes to limiting energy loss and an effective way of improving overall comfort indoors and increasing energy efficiency. Since the basement floor is sitting directly on the ground, it's prone to various issues, such as humidity, which spreads to the rest of the house and promotes fungus and mould growth, as well as heat loss due to drafts. All of this can result in poor health and serious damage to furniture, as well as higher heating and cooling bills, and overall utility costs.

Therefore, it's important to insulate your basement floor to improve the thermal performance of the structure and avoid moisture damage. Furthermore, it helps maintain the structural stability of the building as does increasing the value of your home in the event of a future home sale, since you can create a new living space in the basement (bedroom, playroom, etc.), or even convert it into a garage, cellar, storage area, etc. The possibilities are endless!

Basement Floor Insulation: Pre-Insulation Steps

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Prior to installing insulation, it's important to consider a number of variables to ensure that the insulation is both effective and long-lasting.

Measure the level of ground moisture

Before installing insulation, check the humidity level in your basement. If the humidity level in the room exceeds 60%, you'll need to renovate the room before proceeding. If the humidity level is excessively high, your insulation might not last very long and might deteriorate over time. Furthermore, it wouldn't be practical if you want to convert it into a living space, because living in a room with a too high level of humidity is never a good idea.

Hire a professional to assess the situation. They'll be able to determine the humidity level in your basement and suggest an appropriate course of action to alleviate it, and then proceed to install your insulation.

What kind of thermal insulation to use for flooring

Considering that basements typically have high humidity levels, it's important to choose insulation that isn't prone to rot. That said, there are three main categories of thermal insulation for basement floor insulation. Your options are:

• Mineral insulation: These are the most popular insulation option on the market, mainly because of their excellent quality/price ratio. For example, you can choose rockwool, which is best known for its excellent thermal performance, or glass wool.

• Natural insulation: This type of insulation is valued for its eco-friendly nature, and is made from natural fibres derived from animals or plants. However, they're not affordable to all; this material is rather on the expensive side. Examples of this type of insulation include sheep's wool and expanded cork board, which, on top of having the best thermal performance, is a good soundproofing material.

• Synthetic insulation: These materials are derived from petroleum products. Despite their non-green nature, they're still very sought after due to their excellent thermal performance and soundproofing. Among these insulations, one finds polyurethane panels and expanded or extruded polystyrene.

Choosing insulation shouldn't be done at random. You should make a choice based on the characteristics of the insulation and whether it meets the conditions of your basement. Therefore, consider the following:

• Insulation type: natural, mineral, or synthetic;

• Thermal performance of insulation, meaning its thermal capacity, R-value;

• Condition of the home;

• Type of surface to insulate;

• Soundproofing.

If, in spite of these guidelines, you're having trouble finding the right insulation, the best thing to do is to consult a professional, they'll be able to advise you on the best option based on your needs.

Note: For basement floor insulation, it isn't advisable to use natural insulation materials such as wood wool insulation, as it’s extremely vulnerable to humidity. Instead, opt for synthetic insulation such as extruded polystyrene panels.

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Insulated Basement Flooring: The Best Installation Method

When it comes to installing basement floor insulation, it's best to have an experienced professional handle the work to ensure quality and lasting results. If you still want to do it as a DIY project, here are some guidelines to help you.

Carefully cut the insulation

In order to guarantee optimal thermal comfort, the thickness of your insulation must meet the required standards. The minimum thermal resistance must be R = 3. Therefore, you have to cut your insulation according to the right dimensions. Note that these dimensions vary according to the kind of material you chose. Below are the ideal size (thickness) of some basement floor insulation materials:

• 12 to 20 cm for cork;

• 11 to 17 cm for rockwool;

• 10 to 15 cm for polystyrene;

• 7 to 12 cm for polyurethane.

Insulation installation

Installing the insulation is relatively simple and done from atop the floor. Simply lay it on top of the existing bare floor. Then, cover it with the flooring of your choice; you can opt for parquet, tiles, or laminate.

It’s important to adequately clean the floor prior to laying the insulation. To improve the overall performance of the material, we recommend spreading a layer of sand between the ground and the insulation to prevent the material from ripping.

Also, to ensure good thermal insulation, we suggest laying a vapour barrier between the insulation and the flooring. In fact, the vapour barrier will act as a protective film, thus shielding the surface from water vapour infiltration in the basement, meaning reducing the risks of condensation. The vapour barrier will also protect against the humidity contained in the basement.

Even though it isn't essential, you can also install a free-floating screed on top of your insulation. It'll reinforce the material's insulating capacities.

Cost of a Basement Floor Insulation

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In Quebec, installing a basement floor thermal insulator is an expensive endeavour. However, the costs vary depending on whether hired professionals carry out the work or not, the type of project (construction or renovation) in mind, and material costs (these vary). Basement floor insulation is easily done during the construction stage, as it doesn’t involve as many expenses as opposed to the renovation stage. Moreso, the material cost will be more or less expensive depending on the chosen material. Account for:

• $2 - $4/sq. ft. for an expanded polystyrene panel;

• $3 - $7/sq. ft. for an extruded polystyrene panel;

• $2 - $7/sq. ft. for rockwool insulation;

• $1 - $6/sq. ft. for fibreglass wool insulation;

• $3 - $8/sq. ft. for spray polyurethane foam insulation.

Should you hire a professional, labour costs will be established by them. However, you can compare quotes to determine if you're being charged a fair amount. You should also budget for the necessary supplies to install the insulation (staples, glue, vapour barrier, etc.).

If you'd like to learn more about basement renovations and protecting your basement against water infiltration, read our articles.