This article is about a problem you’ve likely encountered: Have you ever walked on the floor of your lounge room in July and thought you were on an ice rink? You already know what the issue is. One of the most underrated comfort issues in your home is flooring, and it accounts for a significant amount of heat escape during wintertime or heat gain during the summer. This guide will take you through what underfloor insulation does, why it matters (more than most homeowners think), and how to decide what is best suited for your home.
What is Underfloor Insulation then?
Underfloor insulation is simply insulation placed between the underside of the suspended timber or particle board floor and the ground or subfloor cavity below. Homes constructed with stumps, bearers, and joists (not a concrete slab) benefit most, as the open space below creates a wind tunnel for cold air.
Typically, netting or clips secure the insulation in place, or rigid batts are snugly fitted between the joists. If executed correctly, it will produce a thermal barrier that keeps the inside temperature much steadier regardless of what is going on outside.
Why Bother? The Real Benefits of Underfloor Insulation
You are probably thinking the only benefit of this is staying warm, but it is more than that:
- You’ll save money on power: If your heater is not forced to work as hard, it will reflect on your power bill, as less heat will be lost through the floor.
- You’ll get a consistent temperature: You won’t need to change the thermostat over and over again, and an insulated subfloor will keep the temperature for longer.
- You’ll have reduced draughts: Cold air seeps through gaps in flooring. This can be eliminated with insulation and good draught-proofing.
- Your moisture will be in control: Some insulation products can also control condensation in the subfloor cavity that can cause mould and timber rot over time.
- A move towards a higher energy-efficient rating: When renovating or building, floor insulation is part of your home’s overall thermal performance, so it can help when you come to have a 7-star energy rating certificate.
Do you really need it?
Are you still wondering if you really need this flooring, or if it will be okay even if you don’t? We have got you covered; the following is the list explaining why you need underfloor insulation:
If you live in an older weatherboard or timber floor house, especially before the 1990s, you likely have very little or no insulation beneath your floors. Usually the largest gainers, homeowners can often feel the difference after the first night of cold weather following installation.
If you are getting a renovation or an extension project done, this is the perfect opportunity to install underfloor insulation when the floor is either being exposed or removed. It’s more cost-effective to do so during a renovation than to modify later.
If you are planning to build new, the building will probably have minimum thermal performance requirements anyway, so talking to your builder at an early stage will benefit you much more.
If your home sits on a concrete slab, then obviously underfloor insulation won’t fit in the traditional sense, since there is no accessible cavity. Hence, in this case, your energy efficiency gains will come from ceiling and wall insulation instead.
The Installation Process, Step by Step
It is important to know the process so you have realistic expectations, particularly when looking at a variety of quotes from different installers.
- Subfloor inspection: Before anything is installed, a technician would check the clearance height, moisture content, and condition of the bearers and joists.
- Measurement and choice of materials: The cavity is measured to determine the correct thickness and type of insulation to fit snugly.
- Fitting the insulation: Batts or blankets are cut to fit and are fastened between the joists, typically with netting or support wire.
- Sealing gaps: If there is any obvious draught around pipes, vents, or around the floor edges, this should be treated at the same time as the pipes or vents are being insulated, as gaps in airflow won’t be fixed with insulation alone.
- Final check: When walking through, there should be no sagging, gaps, or compressed sections of insulation, as compressed covering does not perform well.
They can be accomplished in most standard homes in a single day, although larger or more difficult-to-access subfloors may require additional time.
Which Material Is The Best for You?
There are several standard choices available, and each works well for slightly different situations:
- Glasswool batts (including products such as Earthwool ceiling insulation for use under floor) are a common balanced approach product. These are widely available, affordable, and provide reasonably good thermal performance at a moderate cost. One of the most notable features of Earthwool is its production using a bio-based binder, making it less irritating and dusty to handle during installation.
- Polyester Batts: These are slightly more expensive and are also an excellent choice for homes seeking formaldehyde-free covering that is a bit less irritating to sensitive skin.
- Reflective foil laminate is effective in warmer climates or as a second layer that reflects radiant heat, but it does not necessarily have the highest insulating value on its own in colder climates, and it is not as effective as an air gap.
- Rigid Foam Boards: In homes with very shallow subfloor clearance, a rigid foam board is the only way to get a good fit for the batts.
For most timber suspended floors, if you’re looking for comfort, affordability, and easy handling, an Earthwool-type glasswool product will be your best choice. If the budget is not an issue and you are looking for maximum sustainability, then polyester should be considered.
Some tips to keep in mind when installing
- Don’t compress the insulation to force it into a tight space. It is advisable to cut the batts to fit rather than squashing them together, as they lose many of their insulating properties when squashed.
- Provide sufficient clearance around exposed wiring and around recessed downlights, as some products require additional space to meet compliance.
- Inspect the subfloor before installation for moisture issues. If it is moist to begin with, then adding insulation on top of the area only serves to “seal in” the moisture.
- If pipes extend through the subfloor, treat them separately as well from the subfloor to prevent pipes from freezing or losing heat without the subfloor protection.
- Be sure to check the R-value is appropriate for your climate zone. Products labelled for a mild coastal environment may not necessarily perform the same in a cooler inland environment.
What nobody tells you about “DIY” underfloor jobs
Many people believe that underfloor insulation is as simple as putting up a blanket and ideal for weekend renovators; however, this isn’t the case. The reality is that subfloor areas can be small and dark and house surprises such as old wiring, insects, and an unexpected amount of moisture. If it’s a professional or rushed install, it can negate most of the benefits and, worse, can cause moisture buildup against the timber joists. One of those jobs that, from the outside, seem like they’re very easy but need an adequately trained eye to appreciate under the hood.
Putting It All Together
While underfloor insulation is not the flashiest of home improvement projects, it is one of the few home upgrades that pays for itself year after year through comfort and reduced running costs. When taking steps towards a 7-star energy rating certificate for a renovation, fixing cold floors, or achieving a more stable indoor climate, it’s a crucial step that shouldn’t be neglected: achieving the right subfloor.
When considering your options, it may be helpful to have a professional inspection of your particular subfloor before deciding on a material or installer, since clearance height, climate zone, and existing moisture will all determine what “best” actually means to your home.
Ready to prevent heat loss through floors? Book a no-cost subfloor inspection with us, and we’ll walk you through the best insulation fit for your house.