I’ve been looking at ways to make a 1960’s house that I’m in the process of buying as energy efficient as possible. I’ve not reached any conclusions, but this seems to be the place to start… Insulate, insulate, and insulate. Loft, walls, floor and windows. If I get this right first, then I can think about which heating system to go for. Given the house is mainly brick cavity with suspended timber ground floor I’m considering the following options. Any ideas for better ways to do things would be appreciated. Also any books that specialise in opportunities/problems while "updating" properties – I’ve read the bibles and whilst filled with info, they focus mainly on new build.

Floors
Get the floors up, affix under panelling, fill with warmcell. Or is it better to go with a 2 ply expanded foam over the current boards laid to stagger the gaps. (Losing > 100mm of room height?) I’m considering underfloor heating for the downstairs so this may make more sense. What thickness is effective? I.e. I’ve seen the UFH companies now have 15mm insulation containing the channels for the pipes. Doesn’t seem thick enough to me!?

Walls
Get the cavities filled with expanding foam with the least GWP and 0 ODP. This should provide a more air tight seal than beads or blown fibre – correct? Once this is done I should end up with a U value of 0.5-0.6 so not good enough. Therefore I need to consider external insulation. This will be expensive but could get me down to a U of 0.15. (Been playing with spreadsheets to work it out). As I have a 60’s house with some cross wall type panelling, now replaced with UPVC :-( I think I will need external insulation anyway as it’s can’t be cavity filled. I think I have 2 problems with external insulation, 1) Changing the appearance of the house. 2) Getting the detailing correct. Probably need to engage a designer to see what the effect will be like. Would be nice to sell / give away the upvc panelling and replace with cedar/larch etc. However it’s on an estate and may stick out a bit!? I have considered using brick slips, to stick on the insulation, trying to keep it as it looks now, but is that just bonkers? Maybe not for the front, and then render everywhere else. I don’t mind having unpainted wood in the infill sections as I think that looks quite nice. Is it cedar that eventually goes to that nice silver grey colour?

Interested to hear from anyone who has used external insualtion on a private house. I know it’s common on prefab council houses, but not sure on cavity construction, and how it would work with downpipes, window openings etc. I think this is where the costs will creep up - way above the costs of the actual product . i.e. in Labour, so is ti possible to fit on a DIY basis? Or even take the installers course and then do it myself?

Loft
Top up to 300mm with warmcell. But, how can I keep the space for storage? Use I beams laid at a cross to the current joists? Use kingspan insulated flooring boards?

Windows.
Currently uPVC standard glass double glazing. Consider adding a secondary glazing pane (to make it triple) with a low-E pane or I could try the stick on Low E film.

Is it possible to retrofit cavity closers or is the work involved not worth the effort?

Flat roof extension. :-(
Built in the mid 60’s so guessing it has no insulation. This either requires the mess of insulating from inside and finding a way to fill with warmcell, or going outside, and having a new warm roof construction built. (Maybe topped with grass?) Alternatively – would it be cheaper to go with a new pitched roof?

This really onlly leaves draft to sort. I'll be taking out the 60's gas fire chimney, and replacing either with a sealed flue wood burner, or nothing. Need to convince myself on wood yet, but it may make a nice feature - even if it's never used. Adn would provide a backup if the leccy is ever off.

Hopefully having done all that, I’ll be left with a house that needs less than 5kw when it’s freezing outside. Rather than the current 20kW it takes now. You should see the size of the radiators something that made me think they’d be ideal to run with a heat pump – but that’s another story.

Is anyone aware of any software (free!) that lets you model your house? Something that’s a bit better than playing with spreadsheets and can let me input costs of each method to work out cost effectiveness. Or do I need to get a SAP expert in. I should add – I’m an Accredited Domestic Energy Assessor (don’t start!) – but the software we use it too limited do this kind of “what if” analysis I need. It doesn’t let you enter your own U values, and doesn’t have any specific costing – other than an average amount for each type of thing you can do. Hence why it’s called “Reduced Data” SAP. RDSAP for short.

Cheers

Simon

Sounds like you dont need us! Beware of cost effectiveness it sometimes is not a relevant consideration in green terms.

Floors, go for taking them up and dont forget to make good and sure that there is no air leakage on the new ones.

Walls, With external insulation, which is a great way to go, you wont need cavity closers. You can do external insulation on a diy basis sounds to me like you would be capable to take it on. Some details are worth thinking out carefully before the off. Oak tends to go silvery, cedar stays wood coloured unless severely exposed. I have advocated brick slips before on here and got laughed at, they are expensive though.

Replace the flat roof with pitched. sort insulation at the same time.

What is your heat loss when it is 18 inside and 8 outside?

Interesting the big rads like you say heat pump could work -- that is if you need heating at all. may be the people and the light bulbs will do all the active heating you need?

Where is this house? I'll come and help if is within walking distance of me.

Dead nice to hear from you -- we wish you success and we need more like you on here. Please let us know how it goes

Paul: Thanks for the link, Will give it a go. Looks like it might be of use, but I'll have to check if it's making any assuptions based on the canadian style of housebuilding (like being insulated timber frame perhaps!).

I did come across this for people in the UK (or specifically Eire), it's the equivalent of what we have in the UK for doing energy assessments, but requires a lot more training, and will take much longer on site to do the energy assessment. However, it looks like it will allow me to play with it and try different things out as it's spreadsheet based...

http://www.sei.ie/index.asp?locID=1011&docID=-1

Also when energy certificates for commercial building start the UK gov has developed this which they're giving away free (shame they didn't do the same for domestic properties), I shall be having a play with this too, to see if it's over complicated for domestic or a joy to use.

http://www.ncm.bre.co.uk/

Tony - I'm aware that I may be onto a losing battle with some of the costs, however I plan to stay put for 20 years (maybe!) so am willing to take the hit. I've read absolutely loads about climate change and peak oil, so am pretty convinced getting the house sorted is more important than a flash car! It's why I trained to be a domestic energy assessor. There's more than a few of us who were interested in saving the planet. However a large number are in it for the money !!?? Are they going to be surprised - training companies were advertising £70k salaries, which considering it's a 12-16 week distance learning course is ridiculous. I though that if you make 25k your doing well.

18 degrees inside. :-(, I'm still getting used to 19, but I know it's the sensible option. Once I got my head round U values and the kW needed to maintain temp, the extra energy required per degree jumps out at me. I haven't been able to do the calcs yet as we haven't taken ownership to get proper measurements. The 20kW estimation was based on that it will be worse than my current 1995 house which has a 15 kW boiler. Any reason that you chose to use 8 degrees outside? The software I'm using for my DEA work assumed a 19 degree difference - as in 0 outside, but with 21 in the lounge! And I'm in Lichfield (or will be). IS it the mean winter temp or something - so you can size based on that and then stick some secondary heating in for when it does get cold? (Or dare I suggest - leave the old 65% efficient gas boiler in as a backup, but only start the pilot when it gets cold!).

Chuckey: What a great idea, even if it turns out not to be possible it will be the first thing I try. Hopefully the joists are running across the short length. I think this will help until I've recovered from the costs of moving, and can afford a new room in the roof extension ;-) with pitched roof. I've gone all grand designs in my head, extending the run of the current pitch to create a huge south facing mono pitch to cover in solar h/w and pv. But then I remembered planning permission, and how much PV costs!

Which reminds me - keep an eye on www.nanosolar.com. Apparently they're due to slash the cost of PV down to 1/3 or 1/10 of current prices depending on yields. They've come up with a continuous printing process, rather than wafer fabrication methods. So I won't be buying any PV this year!

Simon.

Posted By: SimonHGet the cavities filled with expanding foam

On no account do that! Unmessed-with unfilled cavities are a great asset - keep them that way!Or rather fill them with something massive and fairly conductive, so the whole of your other asset, thermally massive masonry, all 2 skins of it, plus the bit you'll fill the cavity with, are available to the interior. Cavities that have already been filled should be avoided, as a puny half-measure that just impedes the kind of serious means that are now available to us, to make most of the building stock low-, zero- or negative-energy, which certainly depends on massiveness. All your wall insulation should be external to the masonry mass. There are rendered systems, there's a skin of straw bales - and on a current project we're just about to do it with multifoil insulation (35dp battens, non-stitched (spotwelded) multifoil with inner foil most carefully sealed as vap barrier, 35dp counterbattens, rendermesh, roughcast render.

Posted By: fostertomOops, that's provoked a sudden re-think just in time, maybe that should read "stitched (multi-perforated) multifoil so as to be vapour-transparent". Any opinions, other than 'multifoil is rubbish'?

Why would you want vapour to get into your walls from the inside? You had it right first time when you said to use the non-permeable foil that's carefully sealed as a vapour barrier. In an airtight building, water vapour is best controlled through proper ventilation.

Paul in Montreal.

Should have said - that 2.2kw final demand was down from an intial 17.2kW! Startling, so I can't wait to get started and see what the reality is! It would mean estimated bills down from £1,000 a year to £125. Excluding hot water and appliances. But I'm now seeing why insualte insualte insulate should be more of a focus for any government than renewables.

Assuming cost is circa £10,000, payback is 11.5 years. Better than I was hoping for (in fact I didn't expect one!)

It really is important to do this first, so we need less renewables to heat our homes.

Simon.

Posted By: Paul in Montreal

Posted By: fostertomOops, that's provoked a sudden re-think just in time, maybe that should read "stitched (multi-perforated) multifoil so as to be vapour-transparent". Any opinions, other than 'multifoil is rubbish'?

Why would you want vapour to get into your walls from the inside? You had it right first time when you said to use the non-permeable foil that's carefully sealed as a vapour barrier

It's the vapour barrier versus 'breathing wall' question. Note that the vapour's already 'into the wall' from the inside, right through the filled-cavity masonry, out to the external multifoil - no problem, as the masonry is all at internal temp, so hopefully well above dewpoint. Question is, what do with the vapour there, only 30mm from outside air - vapour-seal so it can't enter the multifoil, or make the multifoil vapour-transparent so the vapour can make a quick dash for outside. The inner layer (masonry) should have the requisite 3-10x the vapour resistance of the multi-perforated multifoil.

How about filling the cavity with pebbles to make a rock heat store, and heating with solar heated hot air?
Using one of these for example?
http://www.solarventi.co.uk/index.pl?art=20

This kind of approach might solve the problem raised by Paul (Montreal) in another thread about insufficient insolation in the UK to be worthwhile for space heating. If you suck the thermal energy in, as hot air and actively store it in a large mass, using the air as a transport medium?

Would that work? or is there a calculation that proves its a non starter?

Peter

>Peter, is what you're suggesting a way of taking heat from surfaces and/or airspaces elsewhere that have picked up solar gain, transporting it by air movement and dumping the heat into the mass of a cavity wall by means of a large-surface-area heat exchanger in the form of pebble fill?

Yes I was suggesting this, but I have a lack of detailed knowledge, figures etc.

My gut feeling is that there is lots of solar energy falling on a house, even in the UK winter, from the sun. But if we simply put a window with some thermal mass inside, the mass will heat rather slowly, and if it does reach a good temperature, further insolation will not be stored. We need to keep 'sucking' the solar energy into a large capacity store, it will be at a low temperature and will keep on collecting heat from warm air. That heat will be available by conduction through the walls.

I see the parallel with supply air windows. I suppose they were designed to solve a slightly different problem - supplying fresh air without it being cold and draughty, and at the same time mitigate against the energy lost by mass transfer when the draught has to be heated. That system seems to me to be very promising.

I was suggesting a way to possibly capture much greater amounts of solar energy, but I am aware this is not a new suggestion, why would it not work?
Perhaps because the amount of energy involved does not justify the capital cost? Does anyone know how to calculate this.

Just a thought,

Peter

Hi Tom,
No, I think am thinking of the first, sorry my fault for not communicating very well.

I am suggesting:

1.a solar panel of some sort (outside the house) heats up some air ( I was thinking outside air but I suppose could be in a conservatory/sunspace)

2. The air is piped into the wall cavity filled with pebbles (solar powered fan?).

3. The pebbles in the wall cavity pick up the heat.

4. The wall of the house is now storing the energy as low temperature heat, this will be transferred into the house by conduction/radiation

Of course it would be important to insulate the outside of the wall (external insulation).

My point is that we could have a way of storing heat from the sun, but not at the point of insolation, therefore we could perhaps capture more of the energy striking the collector. If the collector is just a floor or wall behind a window, it will only absorb a small amount of energy too slowly.

But how much energy could we capture in this way? How many watts strike a 1square meter collector in the UK during the heating season?

And how much of that could we store as low temp heat in the wall?



I don't know how to do the calculation.

I am sure people have tried this sort of thing before, in the states, but I suppose i expectsomebody to prove it is impractical by some calcs.

Peter

Hi Simon,

I am sorry, I did not intend to hi-jack your discussion.

I am fond of speculation, much less good at detailed / specific implementation.

But I am not sure about the practical difficulties you mentioned. I see the need to drill some holes into the house walls from the inside, probably under the floor, to let in some pipes. At the top? let the air exhaust to the outside.

But of course I see the problem, what happens when there is no sun and the fan is not driving air through? - It will all reverse and cold air will cool down the pebble/wall. That would be good if it was summer maybe and we needed cooling, but what about in the winter - need a way to close the pipes when it is cold? How about some sort of valve arrangement, if the air flow reverses the valve closes?

Hmm.. I am still feeling there must be a way to capture the sun striking a house in winter and use it in space heating, other than just having some south windows.

Apologies again for misdirecting this discussion.

Peter