internal / external wall insulation

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  • internal / external wall insulation
  • creamegg
    Member

    If your having internal insulation you don’t need a specialist company. A general builder will be able to do this. All it is is a plasterboard with integral insulation layer on the back. This can be stuck to the wall using adhesive or screwed to battens.

    I’ve no experience of the external insulation system.

    Premier Icon Stoner
    Subscriber

    Thermally, external insulation is preferrable so as to put the thermal mass (structural wall) inside the insulated envelope. This means that the heated fabric of the house acts as a temperature buffer/storage during the winter months and can also help keep a home cooler in the summer months. However adding insulation externally is harder than doing it internally. Most eaves and verges of roofs cant take much extra wall thickness before the no longer overhang the wall top sufficiently. The roof line can be altered to accommodate, but it’s obviously a much more involving job.

    External also requires a further weather cladding of some sort. I rather like the idea of taking the opportunity to use a local softwood cladding timber cladding – breathable, recyclable, replaceable at minimum cost.

    Both approaches obviously add to the thickness of the wall itself – by anything from 4″ to 10″ which means doors and window reveals deepen reducing light penetration.

    We have reveals nearly 500mm deep but it’s not too bad.

    Appropriate use of vapour barriers and air gaps will be needed to manage moisture movement as well.

    Im helping out at a house refurb at the moment that has had around 50mm of polyeurethane foil backed board installed inside a sold brick wall – it will really help the thermal performance of the house and its noticeable just through the heat and vent loss calcs how much smaller a radiator is needed compared to in an un-insulated room.

    b r
    Member

    Has anyone had this done, and any companies to reccommend? I know its a lot more expensive than cavity wall, so does it make a decent improvement to heat loss?

    Our walls are the best part of 3′ thick and when I had to make some changes I just built a studding wall. First 50mm celotex, then 50mm studding with another 50mm of celotex wedged in, then a poly sheet and finished with plaster board. It made hellva difference over the week I did it.

    Also, what internal wall ‘coverings’ have you at the moment?

    lakesrider
    Member

    Stoner, – who did you use for the external insulation

    With internal, can you just do a couple of rooms, or does it have to be all the rooms or does this cause problems with other areas of the house? We have a few that lose heat a lot quicker due to their position and construction.

    lakesrider
    Member

    br – internal at the moment is plasterboard (+ some tiling in bathroom)

    lakesrider
    Member

    Cant get cavity wall insulation in our house so am looking into either internal or external insulation.

    Has anyone had this done, and any companies to reccommend? I know its a lot more expensive than cavity wall, so does it make a decent improvement to heat loss?

    thanks

    Premier Icon slowoldgit
    Subscriber

    If you do internal, do you get colder zones and condensation where inner (solid) walls meet the outers? do you have to wrap the insulation around the corner some?

    BlindMelon
    Member

    I work in external facades. Realistically you need around 50mm of phenolic insulation for a significant thermal improvement. This can be clad with a thin coat render of around 8mm so you are adding approx 60mm to the thickness of the external walls. Contact your gas and electricity suppliers as you might find they can offer a green deal payback option. Eon certainly are at the moment.

    Some contacts:
    http://www.wbs-ltd.co.uk/ewi-refurbishment/

    http://www.structherm.co.uk/Refurbishment/External-Wall-Insulation.aspx

    Home

    bajsyckel
    Member

    Stoner – a lot of what you are saying makes sense for many, but assumes certain types of construction, certain occupancy patterns and location etc. There are loads of factors to take into account, but basically…
    is the construction heavyweight (e.g solid masonry/rubble), lightweight (timber/ steel) or hybrid?
    What is the occupancy pattern? out at work during the day? around the house all the time using all spaces?
    Are you able or currently making use of any “passive” heat gains (for example orientation of openings for solar, residual heat from appliances and occupancy…)

    All of these make a difference to where the insulation might be best placed from a purely technical point of view. Then there may be practical constraints – changing appearance externally may be subject to regulation/ impossible or costly due to other construction methods as you note, interior layouts and existing services may make internal changes costly and/or impractical. Then you have things like heating systems etc., etc., etc… Basically what works for one person might be quite different to what is best for their neighbour.

    Slowoldgit – position of insulation (external or internal and assuming it works) should affect the temperature gradient of the built fabric – imagine a cross section through a wall or roof and the temperature inside to outside changing gradually. Moisture will condense at different locations across this gradient. If the construction is “cold” (to use a tech. term) then it is likely to be somewhere in the construction. This may not be a problem depending on construction type and the effect moisture has on its integrity and so on. Moisture shouldn’t be condensing inside the occupied spaces in any event as your furniture, clothes, books etc will go mouldy and it’s not good for your health.

    Following what BlindMelon says about being realistic about what you need to do to make a noticeable difference, I’d say check current German recommendations for insulation values for the overall wall construction. You can calculate composite values online on a few sites. If you are going to the trouble of internal/external insulation (which can be disruptive) you may as well make a hell of a good job of it (insulate as well as possible, make sure the fitters know what they are doing) as the materials are generally less cost than labour etc. and you will always make the money back if you stay in your house for a reasonable time.

    konagirl
    Member

    You can calculate composite values online on a few sites. If you are going to the trouble of internal/external insulation (which can be disruptive) you may as well make a hell of a good job of it (insulate as well as possible, make sure the fitters know what they are doing) as the materials are generally less cost than labour etc.

    +1

    If your plasterwork is in need of work, if you go back to brick under the Building Regs you must then insulate (search for “thermal element”).

    Our house has some very old external polystyrene insulation+render. But even considering how poor it is compared with modern insulation like the phenolic BlindMelon mentioned, it allowed us to meet the Building Regs requirements with shallower internal insulated plasterboard.

    I am sure that insulating internally has made a big difference to the comfort of the rooms insulated (more consistent temperature, seems to heat up and retain heat better).

    slowoldgit, with the internal insulated plasterboard, you just cover the external walls, but include insulated board in the window recesses. That can be interesting if your window frames are quite tight in the recess before adding the extra width internally.

    UrbanHiker
    Member

    bajsyckel, and others, there seems to be a lot of knowledge here, but where does one go to find out the specifics of a particular house construction, usage patters etc to make the decision on the way forward??

    I’ve been putting this decision off for a good 10years, because I’ve not found anyone/anywhere that give me confidence in the information. I’m looking at internal insulation of solid stone walls, and to say the advice is confusing/contradictory is an understatement.

    Just for example, my builder just emailed me suggesting that I should paint the entire external walls with a moisture barrier silicone as then you don’t have to install an internal moisture barrier. It doesn’t come more contentious than that!

    hammerite
    Member

    Lakes – be aware that internal can cause a fair amount of upheaval while the work is being done, then additional time to redecorate internally. Housing associations have been known to send their tenants on holiday while the work is being done!

    External is less upheaval for you, but is relatively expensive, especially if you have some external features you want to replicate/retain.

    However, in both cases try and use someone who is Green Deal registered. You may just want to pay for the work to be completed and not use Green Deal…. but you can get some ECO funding to help pay for the installation (funding has been hard to get for EWI until recently)

    hammerite
    Member

    oh and while I think about it there’s a cashback scheme promoted by the government at the moment (available until the pot runs dry) which will give you back an additional £650.

    b r
    Member

    Just for example, my builder just emailed me suggesting that I should paint the entire external walls with a moisture barrier silicone as then you don’t have to install an internal moisture barrier. It doesn’t come more contentious than that!

    How they going to breathe? And we’re only talking a sheet of poly otherwise.

    Premier Icon blastit
    Subscriber

    Just to muddy the water a little more I am looking at this
    http://www.lime-green.co.uk/products/systems/internal-wall-insulation

    Living in a old house I worry a little about it being able to breathe.
    So have done a bit of research and like the above system.
    Anyone else used it ??

    Premier Icon takisawa2
    Subscriber

    Just had our house externally insulated. House is one of the Wimpey “No-fines” types, built during the 1960’s. (“No-fines” is the term for the construction method, which is basically shuttered concrete with very little sand (or fine aggregate) used in the mix). Very strong & solid buildings, but thermally very poor.

    House was completely scaffolded. They need dry weather for a couple of the rendering stages so it took best part of a month. Difference was noticeable as soon as the insulation boards went up. Rooms that were prone to damp from condensation dried out straight away. Basically two types of insulation boards, phenolic & polystyrene. Ours is 150mm polystyrene with a silicone render. The external system is ideal, as you basically insulate from out – in, & the inner surface of the wall no longer gets as cold. I have some info sheets on both internal & external on my works pc if interested.

    The funding side is a bit of a minefield to be honest, but it boils down to paying upfront yourself, using Green Deal (which basically puts a surcharge on your electric meter), or ECO (Energy Company Obligation, which depends on circumstances but can be difficult to navigate the various rules, many of which keep changing). Top of the list for ECO are electrically heated homes, especially those deemed in need, low income, OAP’s etc.
    The process usually starts with an energy assessment to assess current effeciency, then a sliding scale of possible savings.

    I’d recomend talking to your local council, as there are a lot of community energy groups picking up on it & the Energy Saving Co-Op are involved with sourcing installers & materials at discounts for bulk etc.

    Hope this helps.

    Premier Icon thetallpaul
    Subscriber

    Hi takisawa. Could you forward me the info sheets please? We will be looking to install exterior insulation in the next year or so, and I’m researching different options at the mo.
    Any idea on approx price per m2?
    email is paul (at) phunter (dot) co (dot) uk. Cheers

    meeeee
    Member

    takisawa – could you forward it to me as well please?

    martindmail-singletrack (at)yahoo(dot)co(dot)uk

    Thanks

    Marko
    Member

    I’ve just started to look at internal insulation myself – external is not an option.

    I started here:

    http://www.energysavingtrust.org.uk/Insulation/Solid-wall-insulation

    They recommend ‘Marmox’ and there is a good introduction to wall insulation on their site here:
    http://www.marmox.co.uk/uploads/product_images/47/InterstitialCondensationIssues.pdf

    It looks to me as if the Marmox 12.5mm board will meet the required specifications, whilst taking up less internal space than a plaster board with a polystyrene (or similar backing).

    If anybody has experience of using this product please post.

    Marko

    hammerite
    Member

    Just to clarify a few things Takisawa has said…..

    Solid wall properties or non traditional (like no fines) will qualify for ECO funding regardless of where you live, or whether you are on any benefits (basically anyone should get some money). If you do live in an area classed as deprived or are on benefits you shouldn’t get any additional money for the insulation works. However, you may get other works funded (like loft insulation, windows/doors etc….)

    You can use Green Deal finance and still get ECO funding.

    There’s also some cashback available at the moment put in place by the government to try and stimulate Green Deal/ECO take up.

    The funding is relatively good, better than there has been before for solid wall insulation. However, the percentage contribution will depend on the system you have installed. If you go for a fairly basic finish (silicone or render/dash) the amount you contribute will be lower. If you want to go for anything with a brick effect/brick slip and want to retain any special features then it will increase the cost to you (although the amount of funding will actually be the same).

    *I’ll declare an interest as I work for a Green Deal provider, but in a team that looks after housing associations/councils.

    hammerite
    Member

    BTW if you want me to give you an idea of what kind of ECO funding you might get let me know. I can only work off averages for your property type though (detachment and no of bedrooms) and not specifically for your property.

    Premier Icon thetallpaul
    Subscriber

    Our house is a 1970 cavity wall build. We have cavity wall insulation, but I’m not convinced of it’s effectiveness. The house looses heat relatively quickly.
    Also we are on oil as our heating source. There is gas in the street, but the previous owners decided not to link up.
    We are in a position to build extensions and refurb the house, but we also want to reduce our heating bills and improve comfort in the house.
    We are looking at MVHR, exterior insulation and underfloor insulation (maybe underfloor heating as well).
    Neither of us is on benefits.
    Do we qualify for any of the funding mentioned above and if so who do we contact.
    Is anyone aware of companies that specialise in these products in the York area?

    Premier Icon thetallpaul
    Subscriber

    hammerite. Just read your latest post (I was a bit slow typing). House is currently 3 beds and detached. Extension will bring us upto 5 beds.

    hammerite
    Member

    TTP – the main bulk of ECO funding is for those properties that are classed as hard to treat. So mainly solid wall, non traditional, if cavity wall funding is only really available if the cavity is narrow 40-50mm.

    Unless…. you are on certain benefits or live in an area that is classed as deprived, then you may be able to get funding for CWI. I can check the area where you live for you too if you like (think my e-mail address is in my profile). If you have CWI already then somehow it’s ineffectiveness would need to be proven.

    Premier Icon thetallpaul
    Subscriber

    hammerite,
    Luckily the village is not classed as deprived, but worth asking the questions anyway to see if we could reduce our costs somehow.
    Just want to wrap the house in a nice big duvet. 🙂
    Cheers.

    hammerite
    Member

    Deprived can mean many things. My village isn’t either and is relatively high up on the list when it comes to employment, education and income. However, it is downgraded slightly based on access to doctors surgeries, post office etc… so not always the case.

    If you’re geeky enough check out the index of multiple deprivation.

    Premier Icon thetallpaul
    Subscriber

    From a study done recently:
    On the overall deprivation scale, where 1 is the least deprived in the country, this parish ranks 12 out of 12706 parishes in England. This means that the parish is among the least deprived in the country.
    Makes it sound right grand! 😛

    Premier Icon takisawa2
    Subscriber

    Info sent.

    Hammerite…could have done with your knowledge a few months ago. 😉

    Finished pic:

    If you look to the bottom left of the wall you can see how much the overhang has increased. They bevelled around the windows etc, to avoid losing too much light. Under the soffits wasnt an issue as ours are quite deep, but they used a cowelling on the gable wall as it went beyond the tile line.


    IMAG0913 by pten2106, on Flickr

    lakesrider
    Member

    has anyone had any work done through the Green Deal system at the moment?

    Who did you use for the assessment, did you use the company doing the work, and how do you pick a company for the work? Is it just a case of picking one off the internet?!

    hammerite
    Member

    Here’s the place to start LR: http://www.greendealorb.co.uk/ Other than that recommendations. Maybe contact your local council for advice.

    I’m guessing that there are few providers who actually have the GD finance packages available yet, but most should offer some sort of ECO funding option and the ability to pay in instalments (i.e. typical finance rather than it being tied to your meter).

    My company are working nationally for some of our offerings, but we don’t quite have our general public EWI offer available yet, we are working on council/housing association projects. We’re providing the assessment, funding and the installation, so a one stop shop.

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