Installing underfloor insulation is one of the best bang-for-bucks you can do. It is easy, simple and well within the abilities of even the most novice DIYer for your home. This guide takes you through the steps for a fantastic install.
Polyester underfloor insulation is almost invariably used when insulating under your floor, as it is . In fact it even comes in precut rolls to make life easy!
Why underfloor?
After your ceiling, your floor is where most heat leaves and enters you home. Unsurprisingly with Melbourne's history of poorly insulating homes, nearly every old home and most new homes are simply not insulated underfloor. The good news is that it's simple, easy, cheap and hard to muck up completing a retrofit underfloor insulation installation.
Before Starting
The only major consideration is that you require access to actually get under your floor - something that older homes can sometimes struggle with. The only check you need to do is get under your floor and check you can physically access the underfloor. Typically we recommend having at least 300mm of space to move around. Which is tight be achievable. Any less and it's simply too hard to get under the boards. Any more and the install just becomes even easier. One other thing to look out for is asbestos - very rare in underfloor situations but still worth being mindful of.
What Rating do I need?
This is a nuanced question and we have a whole other blog on choosing ratings. The short answer is... R2.5. You can choose less and save a very small amount of money or choose more and pay significantly more to get only a marginal benefit. This is becasue the supply chain and manufacturing is geared towards R2.5. The smart choice (and what 99% of people in Melbourne install) is simply R2.5. A great benefit, at a low cost and not over kill or under kill.
How long will it take?
Most underfloor installs can be completed by a novice DIYer within a few hours at most. It's very simple and straight forward.
Tools Required
- Tape measure
- Underfloor insulation to be installed (see our Polyfloor range here)
- Stanley knife
- Stapler
Step 1 - Determine the amount of insulation to order
Get under your house and simply measure out the area to be insulated. Make note of any areas that are inaccessible and exclude them.
Polyfloor comes in lengths, so it's easies to measure out the length of each joist to be insulated. Remember joists are normally 450mm gaps in Australia, and Polyfloor comes in a 450mm width - so you can just sum up the lengths measured. Double check the joist spacing just to be sure it's 400mm wide - most are - cowboy built homes are not.
Then, simply order what you require.
Step 2 - Fit the polyester roll between the joists
Pull out the long length of polyester from the bag, and cut it to the right size. Starting at the furtherest point from the access point and working back toward the entry. Push it up between the joists, ensuring there is no gaps.
Step 3 - Secure the Polyester roll with staples
Staple the side of the batt to the joist to keep it in place. Aim for every 10cm or so, and keep it uniform. The batt should be snug. Be careful not to staple into any wiring, as it will be a shocking experience.
You can also do steps 2 and 3 as you go, if the batts won't 'friction fit' into place.
Step 4 - Cross check and clean up
You're all done! Just cross check you have covered all areas, and have not blocked any ventilation. For pipes and any penetrations into the floor, you can cut smaller sections and secure them with duct tape, if required.
That's it! It really is very simple.
Helpul hints
- Take regular breaks as you're working overhead. Underfloor can be cramped, so give your shoulders a break every few minutes so you don't get a tension headache.
- Take a crawl matt or knee pads for tighter spaces
- Keep the polyester in the bag as you're installing (if space permits) so it does not drag across dirt
What about if the floorboard are not installed?
Then it's even easier!
Simply hang some strapping length wise in the middle of the joist and place the batts in from the top side of the floor. Same rules apply regarding gaps - check there are none. You can also staple them for a perfect fit if there are some gaps.
Next Steps
Simply order your insulation here and start saving on energy bills and have toasty warm feet in winter!
FAQ
Can I use fibreglass batts instead of polyester - they are slightly cheaper?
No. Polyester retains it's thermal properties when moist and all underfloor pests also hate it. This is more of an issue underfloor then ceilings and walls where fibreglass is perfectly fine. You also cannot staple fibreglass batts so they don't achieve the same gap elimination, and also require the additional work of strapping.