Insulating Walls of Existing House?

mr626 on 23/08/2016 - 14:26
Last edited 23/08/2016 - 14:48

Hello all,

Some details about our house:

-Brick veneer construction with tiled roof. Built in 1990s
-No sarking in the roof, but does have roof batts installed
-No insulation in any of the walls at present.
-House is built on a slab

The house is OK at present- certainly not a fibro shack, but I would like it to be as well insulated as possible.

From what I understand, the two main options for insulating the walls would be:

1) Remove the plasterboard and install insulation batts.
2) Some sort of 'blow in' insulation

Option 1 would probably give the best result, but a lot of work / cost involved.

My concern with option 2 is bridging the air gap that naturally exists between the outer brick and the inside wall. I've read in a couple of places that you don't want to bridge this gap as it would potentially allow moisture to transfer from the outside wall to the inside (not that my outside walls get particularly wet- we have reasonable-sized eaves).

Then again, there's quite a lot of 'blow in' insulation products on the market so surely if they had terrible issues they wouldn't be able to sell them?

As an example of the kind of thing I'm considering:

http://www.justrite.com.au/products-and-services/retrofit-wa…

Would love to hear from people that have retrofitted insulation to an older house, what worked, what was cost effective etc. What do you recommend?

Thanks

Home & Garden

Comments

  • ItsMeAgro on 23/08/2016 - 14:36

    I believe modern homes are constructed with sarking-like foil-based insulation in the walls.

    A friend installed something similar (http://www.concertinafoilbatts.com/) when their gyprock walls were replaced (though I think they are a bit misunderstood since the politically-motivated witch-hunt a few years back).

    I don't like the idea of blow-in insulation, but I'm not sure there's much else you can do without removing the gyprock. Maybe cut sheets of sarking to the height of your wall, weight the bottom, then hang it down between brick and frame?

    • mr626 on 23/08/2016 - 14:39

      My house does not have sarking at all. Your suggestion is an interesting one, but it would also be fairly labor-intensive I think.

      • Euphemistic on 23/08/2016 - 15:20
        +1

        And highly unlikely to be effective. Thee will be too many points where you can't get anything between the brick and wall (eg below windows) to make it effective enough to be worthwhile.

        The only way to do it effectively is to rip out ALL the existing plasterboard.

        To keep the house cool you could look at shading the walls, to keep it warm maybe heavy full length curtains on the inside

        • Euphemistic on 23/08/2016 - 16:38
          +1

          Thinking more about that, to keep a house warm, you are better off draft proofing it if the ceiling is insulated.

        • pais on 23/08/2016 - 20:30
          +1

          Yeah I definitely think good roof insulation, draft proofing and even double glazed windows would be a big step forward.

  • oscargamer on 23/08/2016 - 14:44

    what's the house built on? slab? or posts?

    • mr626 on 23/08/2016 - 14:47

      Slab, sorry that should be in OP. Adding it now

      • oscargamer on 23/08/2016 - 14:55
        +1

        in europe they also use an expanding foam

        holes are drilled at points (to suit the house construction), a hose/nozzle is inserted and the foam pumped in as the nozzle is retracted

        maybe this is available here?

  • niner on 23/08/2016 - 15:19

    I live in an old house. I insulated the roof and the house is a lot warmer. INsulating the walls is not necessary if you live in a double brick house.

    My tip is to insulate the roof of every room and plug the holes in your house with foamy material. Anything that will keep the heat in and the cool air out. Insulation also keeps the hot air out of the house in the summer months.

    • Sharp on 23/08/2016 - 16:20

      yes and no. Roof insulation could trap the heat inside the house longer in summer, hence insulation of the walls needed - to keep the heat out.

      • niner on 23/08/2016 - 16:24

        Insulating walls of an OLD double brick house is a massive task. I wouldn't recommend it.

        • Sharp on 23/08/2016 - 16:28
          +1

          The house is not double brick but yes it's a big task and I wouldn't do it.

  • oscargamer on 23/08/2016 - 17:55
    +2

    stopping the sun hitting the brickwork with shade, be it trees etc….

    but in summer, the sun is high in the sky, that tends to miss the walls, but heat the roof cavity

    insulation will prevent the heat coming through the ceiling into the house

    also install a few roof vents/whirly-vent things to exhaust the hot roof space air

    reverse cycle air-con would probably be cheaper than wall insulation

    we installed solar panels and air-con and left the ac running on a sunny day - effectively free cooling ! (must size the ac unit to the solar array output)

    always easier to keep a cool space cool, than to try and cool a hot space

  • FirstNameLastName on 23/08/2016 - 21:40
    +1

    op: regarding 'bridging the gap' / moisture.
    Unsure, but I don't think this has to do with rain/eaves.
    I think this might be to do with condensation.
    ie: if there is a huge temp difference, condensation will form on the inside.. leaving an air gap allows it to form inside the brick, not the gyprock.. that moisture is then vented via weep holes in brickwork.

    (I have one friend who was about to 'patch' his weepholes up, thinking they were a construction error.. but gaps in brickwork are there for a reason.. as I'm sure op knows)

    Whereabouts is the house located?

    If you plan on selling down the track, then I think solar/(ducted)ac/batterysystem will get much more bang-for-buck than re-gyprocking everything.. buyers can't see wall insulation, but they can see solar panels/ac etc.

    keep in mind, blow-in insulation may cause real headaches if you go to run cables/ac through the walls later.

    insulating is great up to a certain sweet spot, but then it suddenly gets a lot more expensive for only a little gain.. walls (except for glassed areas) don't account for much thermal transfer.

    good luck!

    (p.s could try bubble-wrap on all your windows.. apparently this is big in nyc winters :)

  • resisting the urge on 25/08/2016 - 00:45

    The roof tiles absorb and store heat. But they sink it back to the air once it cools in the evening. So the ceiling batts prevent heat radiating downwards in the daytime (making the living space hotter), and upwards at night (making the living area colder).

    The walls are too hard so really a lost cause. As others have said, shade them wherever you can, particularly the Northern wall as it probably gets sun all day, and the East and West sides if they get sun early in the morning/late in the evening. If you have a fence near any of them, perhaps install tall lattices on top and grow creepers. If not, grow tall hedgerows and trees that provide dappled shade. Nothing that will drop branches, so things like bottle brush or augmented gums that only grow 3-5m (these are genetically modified gums that are ornate and colorful). Many other choices too, but think of all the aspects or you may plant something you'll regret.

    Solar panels on the roof are an excellent way to shade the tiles, and whirly-vents that evacuate the air from the roof cavity with the slightest hint of wind. Some people say these don't work, but they do and they last and are cheap to buy, fit and are zero maintenance.

    Another thing you should do, on any exposed roof is insulate under the tiles to prevent the heat in the roof tiles convecting into the roof cavity in the first place. Cut some 30x5mm pine strips into 30cm lengths and with one nail in the middle of each, nail several into each roof joist, positioned parallel to the joist. Now between each joist place a roll of bulk insulation. As you unravel it, turn the pine strips 90 degrees and they will hold the insulation up against gravity. You can use the same principle to fit polystyrene sheets between each floor joist if you want to insulate the floor too.

    You can then go one step further and staple sarking over the bulk, for maximum effect.

    These tricks work a treat.

  • Speckled Jim on 25/08/2016 - 18:41

    I haven't seen this suggested (and possibly for good reason…).

    So, tearing into BV walls to insulate them is a big job, right? Not worth the cost.

    If you don't mind losing a few centimetres from each internal wall, what about insulated board bonded to your existing walls? This is one example, I've seen other thermal/sound boards in the past too. Choice of product thickness too.

    One thing I've done at our BV place is mirror-tint the windows — quite a difference in the summer.

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