The Basics of Floor Insulation

In the present times, insulating may be mainly installed on walls, attics, and ceilings. While these parts of the structure are fundamental to the house, it would also be of very great help if insulation is installed in the floors of our homes. Floor insulations prove to be of great impact and contribution in reducing a household’s heating and cooling costs, providing insulation to the underfloor of a house. Adding floor insulation effectively brings heating costs down, especially for those houses with cellars that are unheated and those houses without basements. 

How does heat travel through floors?

The mechanism in which heat flows in and out of your house’s floors and how your floor holds or releases heat depends on the type of sub-floor your home possesses. Floors such as concrete slabs, which are known for their high thermal mass, will hold and retain heat throughout the day and will release the said heat during the night. Moreover, other types of floors such as stump and joist floors do not retain heat as effectively and thus lose heat very rapidly. 

A considerable amount of heat can be lost or gained through the floor; daily, about 10% to 20% of heat can be retained or released through the floor as the house’s temperature fluctuates throughout the day; insulated floors improve thermal control inside your house.

What are the types of floor insulation?

The type of floor insulation to be installed in your respective homes will have to depend on the type of floor that you have. Moreover, these are the common types of floor insulation:

1. Polystyrene panels
2. Rock wool batts
3. Fiberglass or glass wool batts
4. Polyurethane foam

Some floors may rely solely on the carpet and the layers of insulation it provides, but this may not be an option for exposed floor boards or other present types of bare flooring. In general, it is essential that the floor is sealed properly and efficiently in order for it to have a sufficient and decent insulation. If this is ensured, the R value of your home will surely be boosted and its thermal envelope will be protected well.

What are the other perks of installing floor insulation?

Aside from regulating your home’s temperature and reducing cooling and heating costs, installing floor insulation may bring you more other benefits. 

1) Installing floor insulators prevent the occurrence of drafts in homes.

For one, floor insulators eliminate drafts in homes that are raised above the ground. Because of the installed floor insulation, draft is prevented from entering through the gap that is found between the floor and the ground.

2) Installing floor insulators create a vapor barrier, and thus in turn reduce moisture.

Another benefit of having floor insulation installed in your homes is that it prevents moisture from creeping in and soaking the floor due to its layer of insulation between the floor and the crawl space. Floors made of wood are especially prone to this type of damage. Also, building up of moisture may lead to mold growth, which is very detrimental not only to your floor and to your house’s structure, but also to your family’s health.

3) Installing floor insulators will prevent the freezing of pipes during winter.

In most homes, if not all, the piping is situated beneath the flooring. Installing floor insulators would provide extra protection for these pipes, especially during winter. In countries with harsh wintertime, the pipes under the floor may crack and thus burst if the water inside them freezes. This occurrence may destroy the house’s water system. Providing floor insulation will prevent this from happening.

Floor Insulation - A Quick Run-Through

Moving into a new house with a floor that is not insulated can be a problem if the house has solid floors. The difficulty might be in the materials used because floor insulation for each type differs in work and costs.

Generally, ground floors are done as either solid, usually concrete slabs, or suspended. (These are timber floorboards on joists.) When these are not insulated, the U-value between is 0.45/m2k and 0.70W/m2k. Our target value is between 0.20W/m2K and 0.25W/m2K (depending on floor geometry).

It can be more trouble (and costs more) insulating a solid floor than insulating a timber floor. The payback for the former is 8 to 10 years or more, but the payback for timber floors is between 3 and 5 years. (This is recouping your investment-expense on the insulating work.)

Initial precaution

Sloppy insulation work can result in thermal bridging. Thermal bridging happens where the solid building elements continue from the inside to the outside of the structure, conducting the cold out or heat in. this results in severely compromising the value of work done and leads to cold spots and condensations.

During work, you need to consider the airtightness layer beneath the floor next to walls and round the edges. The airtightness prevents unwanted infiltration of draughts.

Wooden floor insulation

It will be easier to stuff insulation between the joists if there is access from below. Simply press the insulation against the floorboards without having to over-compress them.

You can add more insulation than the depth of the joists would permit in two stages. One is stuffing the spaces between the joists and adding battens to the underneath of the joists. You can then fasten the second layer of retaining boards or netting to them.

The holes in the floorboards (where pipes and wires go through) need to be plugged with mastic and tapes to prevent draughts. If there is a possibility that the room could flood, a damp proof layer should not be put beneath the insulation. (Draught-resistant fabrics should be used).

Concrete floor insulation

Floor Insulation can be added over the existing concrete slab or under a new one. If the insulation is placed above the slab, the room will warm up more quickly when the heating is one. It also cools down easily. (This applies to all internal insulation.)

It affects the floor level which can impact on door openings, stairs and other house fixtures. This is the reason why phenolic foam is the most common solution in cases like this because it can still achieve greater insulation with less depth.

Insulation below the slab is generally better especially in warm south-facing rooms since the concrete helps absorb the heat and can limit the overheating. The damp proof membrane is placed on a layer of sand to prevent being punctured by sharp stones.

Since it also serves as the airtightness membrane, it laps up the sides of the walls to link to the plaster or plasterboard. Floor insulation is usually a more efficient heating than the conventional systems.