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Underfloor insulation

Emma O'Connor
8 years ago
I have a fibro cottage in the foot hills of the Victorian alps. Looking for some advice regarding underfloor insulation. In the coming years I plan on replacing the current fibro shell of the house and put in wall insulation, in the mean time I would like to start with some underfloor insulation this winter. Standing in my large kitchen in winter it is very common to feel the cold air coming up through the floor boards and chilling your toes. Outside Temp can range from early 40's in summer to -6 in winter. I would love some advise from anybody that may have suffered a similar dilemma.
A few things to consider...
*** My house in on a slight hill so the clearance is varied with the majority of the under house area having a low clearance.
*** the house has been built in 3 stages over 80 years so there are 3 different joist widths under the house,
*** I would prefer not to use an insulated roll style product as I've heard negative things about rodents being trapped between floor boards and the insulated fabric and getting smelly.
*** my floor boards are very noisy to walk on so i would like a product that might offer some sound insulation too (don't know if this last point is a valid request) ....

Any personal experience or trade advice is gladly welcomed.

Comments (22)

  • junipergirl
    8 years ago
    Hey Emma, I live in a fibro cottage and have very similar issues. I live in Vic near The Black Spur, so we get variable temps, too. One word of advice before you go pulling off the shell of the house; Fibro is ASBESTOS (just a different name) sheeting! Be VERY careful with how you go about removing it, and disposing of it. Many tips refuse to take it. The name fibro cement (true name is fibre cement) came in a loooooooong time ago to stop people worrying about asbestos. It tricked people but it is not safe as we back then were led to believe.

    Anyways, moving right along. We have been using sound proofing insulation under the house (we are split level at the back) to help with the cold/heat rising through the floors. Putting the same in the walls by removing the masonite interior walls and replacing with fairly thick, 10mm plaster board. This has helped immensely with heat etc in the areas already done.

    The sound thermal insulation proofing batts come in a pack of eight, R2, covers about 4 and half square metres, and cost about $35 each pack.. You can cut them to fit each area of none standard joists as we are doing. What we are doing is using strapping which is nailed in place to hold the batts up, you can then add very small diameter squared meshing as well. This will help reduce rodents and birds getting in under the batts. Yes, it adds to the cost but it is better than a dead rat festering away in summer! LOL!

    If your boards are very noisy to walk on, check the bearers haven't sagged with age, they may need replacing. Your stumps may be rotted at the base too, so you need to check all of them too. This is often the reason boards make a racket when walked on in older houses.
    There are not many options for insulation under houses. My friend has been looking at importing some from USA to start a business. The Yanks sure know how to insulate houses! However the cost to the public would be too exorbitant at this point in time. So we are doing the best method we can think of instead!

    Again, do be wary of ripping off fibro cement off anything!

    Hope all that helps a little!
  • PRO
    Romany Lambert Garden Design
    8 years ago
    Hi Emma,
    We also had draughty floorboards which look lovely but felt like a bit of a colander in winter! We got someone to use spray insulation on the underside and it's worked really well. They would advise you of the minimum clearance you need. We found it made the house feel more solid, I think because it didn't sound so hollow walking on the boards. The impact with heat loss has been better that any other product we looked at and isn't a comfy cocoon for rodents either! Good luck with the project.
  • PRO
    North Shore Design
    8 years ago
    75mm polystyrene sheets would be the best product to insulate your floors, given your restricted head room under your house. It is pretty easy to crawl under a house , take the measurements for one room then cut all the sheets outside. A few nails along each side of the floor joists is all you need to support them.
    You will see some benefit doing this but remember only 10-20% of heat is lost through floors. In a cold climate though, every bit helps !
    As for your floorboards squeaking, that is a result of the floorboards gradually shrinking over the years plus possible nails rusting or coming loose and nothing to do with the stumps. Rotting or settling stumps resulting in uneven floors is another matter so while you are under the house and before you start to insulate, have a good look at all your sub-floor framing including gal ant caps etc that may have rusted out.
    Your best solution is to re-nail all the floorboards down even if you are thinking of polishing them.

    Regards and good luck
  • Daria KT
    8 years ago

    I would strongly recommend you check out www.laros.com.au

    Foam is a small part of overall fixing a drafty house

  • anniewelch
    8 years ago
    I lived in NZ for years and we made sure we had good thick insulation in the ceiling also. I have noticed here in Aussie people aren't so much into it but it makes a huge difference in hot and cold climates. Good luck with your home and I wish we were down your way as the heat up here in Brisbane is horrid
  • PRO
    Melissa Treadgold Architect, Sydney, Australia
    8 years ago
    My advice would be to make removing the asbestos cladding a priority then address your other issues. Th
  • KK1000
    8 years ago
    We live in a 56 y old double brick house. In winter floor is very cold. We have squeaky pine floorboards which I am not going to resend . I have decided to fit floating floor over it. Floating floor require underlay and I hope it would help with cold and may even reduce the noise.
  • Ai Jaedee
    8 years ago
  • Susan Vale
    8 years ago
    We used blue styrofoam board under our last house (weather board home on brick piers) We used Liquid Nails Fast grab to hold them in place with a few strategically placed nails in the joists. Best decision we made.
  • hosinator
    8 years ago
    Hi Emma,

    We live in Canberra, so similar temperatures. We used fibreglass batts, $1500 for 110m2 of space and another $150 for someone to install it. Took them half a day to do it. No draughts and much more comfortable.

    Someone mentioned polystyrene sheets:

    "75mm polystyrene sheets would be the best product to insulate your floors, given your restricted head room under your house. It is pretty easy to crawl under a house , take the measurements for one room then cut all the sheets outside. A few nails along each side of the floor joists is all you need to support them."

    I started doing this and spent a whole day measuring, cutting and covering only 10m2. Biggest waste of time and money, I would stay away from doing this. It's dusty, you're on your back the whole time, there is little to no light and the polystyrene sheets are also unforgiving. If you cut it wrong, too bad. Either cut another sheet or install it with a 2cm gap. The batts fit flush in the space and are very forgiving to work with and if you have any future electrical work, they are easy to remove and replace.
  • zen_garden
    8 years ago
    last modified: 8 years ago
    We too used Earth wool insulation batts. Once pushed in place we stapled chicken wire onto the joists with a staple gun, it keeps it up there and no rodents can get in. Easily removed if needed.
  • clikmania
    8 years ago
    Hi Hosinator - we are in Canberra too - where did you buy your underfloor batts and who fit in for $150? Thanks loads :)
  • PRO
    North Shore Design
    8 years ago
    Hosinator, I don't know what you do for a living but I woudn't recommend you as an insulation installer if you took a day to install only 10sqm. I'm a builder by trade and two of us used to be able to do a reasonably big house in one day - half of it with limited sub-floor space. The styro foam, rated at R3.0 to R-4.0 depending on how thick you want it, is very easy to install and over time ends up being a better floor insulation product than batts which attract insects etc. IMO and I've worked on a lot of houses over the years.
    Regards
  • hosinator
    8 years ago
    Hi Clikmania, It was about 6 years ago that we did ours. It was done by one of the larger outfits, from what I recall It was Just rite in Fyshwick.
  • PRO
    Sarah Lebner
    8 years ago

    You might like to get in touch with Andy Pickard: http://www.ajpengineering.com.au/
    He specializes in home energy efficiency advise and retrofitting particular to the Canberra climate and issues. We have a unique climate in this region - not just because of the extreme temperatures, but also because of how vapor behaves in our walls, which makes choosing the right insulation important :)

    Goodluck! Should be lovely after you've installed it!

    (I work at Jigsaw Housing, the collaboration of architect + builder + scientist, and we specialize in energy efficient homes. I also do casual private consultations for people that are just looking for a bit of design/efficiency advice that's not really worth taking to an architect for a full service.)

  • Dan Shearman
    8 years ago

    yip earthwool way to go


  • Emma O'Connor
    Original Author
    8 years ago
    Thanks everybody for the great advice. :-)
  • suancol
    7 years ago

    I was told place insulation in order of priority from top down in a house because heat rises and most is lost through ceilings. I also advise polar fleece as curtain liners and pelmets for all windows for more winter heat saving and cooling in summer

  • Vanessa Hoyan
    6 years ago
    Any ideas on whether cathedral ceilings can ever be insulated?
  • PRO
    Adit
    6 years ago
    Hi, how is expol as a product for underfloor insulation
  • PRO
    NSW Regional Insulation
    4 years ago

    We have been installing polyester underfloor insulation rolls for the past 15 years without any problems with rodents.


    Best winter and summer insulation ratings, cheapest and easiest to install properly in tight spaces. No itch, hydrophobic and easily stapled to the sides of the floor joists.


    4 Seasons Home Insulation - Ross Kestle