Retro Fitting Wall insulation

Forums › Home Workshop DIY › Retro Fitting Wall insulation - type and cost

Morgenmuffel

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#196703 9-Jun-2016 20:15

Just want a rough idea for an average home cost, obviously taking existing cladding off and doing it is out of the question, we have one wall that is icy cold all winter and its just a pain, we already have roof and floor insulation

I hve seen 2 types of spray in insulation mentioned

1) Expanding foam - seems to have overwhelmingly negative reviews

2) Cosywall or jetstream max- a spray in spun fibre thingie like rockwool - seems to be quite good and doesn't seem to have as many bad reviews

any suggestions on cost

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#1568953 9-Jun-2016 20:24

called and asked them for a quote?

blackjack17

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#1568957 9-Jun-2016 20:27

replacing gib really isn't that expensive

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nickb800

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#1568973 9-Jun-2016 20:39

What sort of exterior cladding do you have and what's the age of the house?

tdgeek

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#1568989 9-Jun-2016 20:58

blackjack17:

replacing gib really isn't that expensive

Far cheaper than exterior work

timmmay

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#1568996 9-Jun-2016 21:09

Replacing gib is INCREDIBLY messy and disruptive to a house. You have to take everything out of the room and keep things moving around the house. Going over the top of old gib isn't so bad.

I have foam pumped into the walls. It made a bit of a mess of the weatherboards, filling the holes is quite difficult to do well, given how many there are. The insulation isn't that effective. I didn't notice much of a difference when it happened.

Doubling up on ceiling insulation I noticed immediately, and I also noticed a little when under floor went in.

richms

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#1569027 9-Jun-2016 21:59

I really noticed the underfloor on the cold feet under the desk, probably the most effective change. The ceiling insulation getting done more than halved the amount of watts used maintaining 24ish degrees in the room in winter, but did nothing to improve comfort, just made it cheaper to be the same hot upper body cold feet situation.

The wall stuff will be a building consent situation so whatever the council need done will have to be done. That is why I have left that un done here till it's reclad time since at that point I will be able to do it, and replace the horrid fiber cement board with leaky nail holes with something with a cavity and decent apperance like linea

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elpenguino

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#1569030 9-Jun-2016 22:10

I saw an audit style report on this insulation - of course expanding foam relies on filling all the enclosures between the studs and nogs.

The audit showed a wall that had been done in this way and then had the gib stripped off a few years later. Filling of sections was incomplete and the wall even had a whole segment or 2 missed because of unevenly spaced nogs.

i reckon if your wall is as cold as you say, you should do it the 'hard' way.

Having just been through gib-based disruption to the house over summer myself, i know, it's a real PITA, but the new-room look and feel is worth it.

When you strip a room you can also do the things that this style of insulation cant do like the thin gaps around the windows or between double studs etc.

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#1569032 9-Jun-2016 22:19

Also you can plane the studs which is something that seemed to not happen in old construction so there was massive uneven bowing on some walls at a friends place when we regibbed it. Sorry, gibbed it because it was that horrible old thick plaster stuff with strings in it. Also ideal time to change baseboards, trim around windows etc to less ugly profiles.

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mdf

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#1569067 9-Jun-2016 22:59

How old is the house? Unless it's sufficiently old not to have dwangs (pre 1920s?) I wouldn't consider one of the blown options. You're far better off doing it once and doing it right. Removing the gib is less painful than you would think.

mattwnz

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#1569081 10-Jun-2016 01:00

I had a quote for the foam stuff several years ago, and it was very pricey. Think it was about 5k for two walls in an old part of the house that didn't have wall insulation. Don't think the company is even around now. Far better cost benefit by just doubling the insulation in the ceiling, as long as you don't have a skillion roof. Can't add much else to what others have said, as most is good advice. Some of the pumped in ones can also settle and/or shrink, and as others have said, they can missed cavities. You also need to factor in filling the holes, and probably repainting the exterior.

If however you are removing gib to install insulation, you should check with your council as to whether you need a consent, and may need an inspector to check the insulation before you install the new gib. Even the pumped in stuff may need it, as you can affect the weather tightness (block cavities etc) of the building. Also some foams shouldn't come in contact with plastic, as they can eat into it. All this can affect your insurance too. So good to check that too. Not getting a consent when you needed one can be major problem if you need to resell the house.

timmmay

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#1569085 10-Jun-2016 05:18

elpenguino:

The audit showed a wall that had been done in this way and then had the gib stripped off a few years later. Filling of sections was incomplete and the wall even had a whole segment or 2 missed because of unevenly spaced nogs.

I have it, I've opened up some walls, and yes some sections are missed - 5% perhaps. Missing sections really reduces the effectiveness.

mattwnz:

I had a quote for the foam stuff several years ago, and it was very pricey. Think it was about 5k for two walls in an old part of the house that didn't have wall insulation. Don't think the company is even around now. Far better cost benefit by just doubling the insulation in the ceiling, as long as you don't have a skillion roof. Can't add much else to what others have said, as most is good advice. Some of the pumped in ones can also settle and/or shrink, and as others have said, they can missed cavities. You also need to factor in filling the holes, and probably repainting the exterior.

If however you are removing gib to install insulation, you should check with your council as to whether you need a consent, and may need an inspector to check the insulation before you install the new gib. Even the pumped in stuff may need it, as you can affect the weather tightness (block cavities etc) of the building. Also some foams shouldn't come in contact with plastic, as they can eat into it. All this can affect your insurance too. So good to check that too. Not getting a consent when you needed one can be major problem if you need to resell the house.

Cost me, from memory, $3K for an average sized house about 5 years ago.

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plod

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#1569117 10-Jun-2016 08:02

I have just started this. Done first bedroom to walls. 5 sheets of 2400 GiB and a bail of insulation. Just under $200. Probably allow another $150 to finish off. Skirts, plaster etc

rphenix

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#1569141 10-Jun-2016 08:56

timmmay:

Replacing gib is INCREDIBLY messy and disruptive to a house. You have to take everything out of the room and keep things moving around the house. Going over the top of old gib isn't so bad.

Your right of course - but it is worth it - you can run new ethernet wiring with the gib off, consider electrical changes, find unknown damage easily, if your removing it from internal walls you can even straighten them a bit with a nudge from a mallet before putting the gib back on the most expensive part is paint.

Fred99

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#1569145 10-Jun-2016 09:03

mattwnz:

If however you are removing gib to install insulation, you should check with your council as to whether you need a consent, and may need an inspector to check the insulation before you install the new gib. Even the pumped in stuff may need it, as you can affect the weather tightness (block cavities etc) of the building. Also some foams shouldn't come in contact with plastic, as they can eat into it. All this can affect your insurance too. So good to check that too. Not getting a consent when you needed one can be major problem if you need to resell the house.

If you're insulating external walls then it's almost certain that you will need consent. There was an exemption put in place by the Chch council for insulating as part of "like for like" recladding of EQ damaged houses (which was also made exempt), but where cladding material/system was changed consent was needed for that anyway. With the pumped in foam, then it's not going to be easy to get consent - as it's got to be shown that the insulation won't bridge between cladding and timber framing, if work has to be done in the cavity (ie to put in some backing material / building paper to prevent bridging), then you're back to square one in needing to gain access to the cavity from the outside or the inside, in which case the most sensible insulation to use would be conventional glass or polyester batts. The foam which eats in to cables is polystyrene - which leaches the plasticisers out of PVC cable insulation turning the polystyrene into goo, and leaving the cable insulation brittle. That's the stuff commonly used in sub-floors ("Expol" etc) - where great care is needed.

I doubt there'd be much point retro fitting wall insulation in most cases in terms of payback on energy savings - wait until you need to re-clad or re-gib, then do it - but then if you're going to do it room by room over time, the consent process may be a complete PITA. I don't know whether council would be happy to come out and inspect once (at ~$200 per inspection) then accept photos or other evidence that the rest had been done properly. If there's no existing building paper then it'll need to be fitted to form a pocket between studs and nogs to hold the batts away from the cladding. That seems to be the usual accepted method - but it carries a risk, that as there's no full building paper, then if there is a leak in the cladding, and if there is something allowing that water to bridge back to the framing, then it's going to sit on nogs and plates - be soaked up by the insulation, and held there - so it's potentially worse than if there was no insulation and free movement of air in the cavity, where there's some chance that water from a small leak will dry out.

timmmay

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#1569147 10-Jun-2016 09:11

rphenix:

Your right of course - but it is worth it - you can run new ethernet wiring with the gib off, consider electrical changes, find unknown damage easily, if your removing it from internal walls you can even straighten them a bit with a nudge from a mallet before putting the gib back on the most expensive part is paint.

It may be worth it for some. When you have a wife who's sick of construction work and wants the house back to normal for family coming to stay it's really not worth it. For us this is an external wall with no plugs, no wiring, just a window and a wall.

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