Hi all,
We've recently bought a six bedroom/three bathroom detached property (built in1986) and have have a one off opportunity to make it green before we move in. However, not being builder and being (shamefully) ignorant of all things green until a few months ago, I have now read so much in such a short space of time that I can no longer see the wood for the trees. If anyone could help me out I'd be very grateful.

My plan for making the house green is to first reduce it's energy requirements to a minimum within the limits of cost effectiveness and practicality, and then look at micro generation. For the first part I have...

1. Insulate all exterior walls.
My builder wants to go with internal wall insulation rather than external because the existing roof has no overhang so external insulation would require taking the roof off. However internal wall insulation would mean I'd lose 10cm from all walls to achieve a U value of 0.17. It also seems quite expensive (we've been quoted £42 sqm) and fraught with installion problems. I'd like to with external wall but wary about what implications that'll have for the roof.

2. Make it airtight.
Well not 100% since then you'd suffocate, but it seems from reading threads here that this is quite important. However I can't find anything that tells me about the practicalities involved. Ideally I'm looking for a work schedule to give to builder so that if they do the stuff on it then the building will be airtight especially since all I have now is the phrase "Make it airtight, please".

3. Mechanical ventilation.
Okay this is where I get a little fuzzy on stuff. If I make it all airtight then building regs will say you need xx amount of airflow here, here and here so you'll need holes, fans and vents. This seems to me to defeat the object of making it airtight, so one way around it would be to stick in some mechanical ventilation and then if you are going to do that then you may as well put in a heat recovery system as well. Is this logic sound? And is it only worth sticking in a HRV(?) if the place is airtight to begin with? What happens if it's not? Do they have to be on all the time, even in the summer, or just the ones in the wet rooms? I'm also worried about the noise they generate. I know some are labeled as silent operation but I suspect that my idea of silent is different from their idea of silent.

4. Space heating.
Now this is where I'm really confused. I was going to go with underfloor heating and a ground source heat pump. But now I've read a couple of articles saying that the efficiency of ground source heat pumps drops the more you push them which means that you lose any green benefit from having them and their running costs become comparable to that of a gas boiler. So now I'm thinking of a condensing boiler with underfloor heating although I have to admit, I really don't have a clue!

Any advice anybody could give would be very gratefully received (even if it's of the go away and read this variety). Like I said, I'm very new to all this, so please be gentle. Thanks

P

Hi Pantasarus,

Sorry I have no clear answers, but I just wanted to say that I am feeling a bit like you. Indeed every householder in the country is basically in this situation are they not?

We know there are many good health/financial/environmental/comfort reasons for greening our homes. The matter appears complex technically/legally/practically. There are significant differences of opinion amongst the experts. Finding an expert to help or advise is difficult.

What we need is a clear set of guidelines about how to 'green' an existing home, for different levels of expenditure. Perhaps we need several, to cater for different tastes and philosophies, and different existing building types.

The Green Building Bible is tremendous, very interesting and a fine piece of work, but it does not solve this problem, it creates as many questions as it solves.

Could the people on this forum not undertake to produce, collectively, a simple document outlining one or two or several general approaches that answer this question?

Perhaps responses on this thread could be the basis of such an undertaking?

As a start , I think that Pantasarus has got the 4 main things in the correct order - Insulate, draughtproof, ventilate and find a way to fill the remaining heat requirement.
Do people agree with that?

Peter

http://www.greenbuildingforum.co.uk/newforum/?CategoryID=16

http://www.greenbuildingforum.co.uk/newforum/search.php?PostBackAction=Search&Keywords=external+wall+insulation&Type=Topics&btnSubmit=Search

http://www.greenbuildingforum.co.uk/newforum/search.php?PostBackAction=Search&Keywords=internal+wall+insulation&Type=Topics

J

Pantasarus,

For a lot of these questions the answer is what gives the most bang for your buck. For ongoing energy costs you can make a simple assumption that CO2 = Money. As with most things in life you can rapidly get into a diminishing returns situation.

1) In an 80's house why is cavity insulation not an option? In fact, are you sure you don't have some already? I had a bungalow of similar vintage and that had glass fibre batts between the habitable bit & the garage, so I'd guess it was all round. I wouldn't go for external insulation if it meant major roof works.

2) Airtightness can be divided into draught proofing (doors, windows etc.) and more structural stuff like completely replacing dry lining with wet plastering. I'd guess that for most existing stock the draught proofing will give more than 50% of the available savings. If you don't already have them I'd say that enclosed porches (air locks) at every entrance door are a must.

3) Sorry, can't advise.

4) I'd suggest that you separate out the heat source (boiler, GSHP...) from the delivery system (rads ...) for planning purposes. Any wet system will give you plenty of flexibility for the future, although you could consider using ducted air heating, linked to the ventilation system you asked about. If you set aside an actual 'boiler room' you could change the heat source fairly easily later. Apart from that, the most important thing is an effective control system. In a big house like yours I would seriously consider a computerised zone control setup, so that room usage can be taken into account.

Good luck.

Hi people,
Thanks for your responses.

<blockquote><cite>Posted By: James Norton</cite><div class="CommentHeader"><span><a onmousedown="quote(17797, 935, 'Posted By: James Norton');">quote</a></span></div><div id="CommentBody_17797" class="CommentBody">'pantasarus' why does external insulation require you to take the roof off !?</div></blockquote>

The builder said it was something to do with the roof having to be extended over the new external insulation. The house is in Bath which requires every building to be clad in bathstone so adding external insulation would mean adding the insulation (100mm?) and then putting new bathstone cladding over that to get past building regs. This would result in new walls that are quite a bit thicker than the originals and would jut out past the roofline. Also I'm not sure what would happen with openings for windows and doors. Does anybody know how expensive it is to extend a roof out?

I am tempted away from internal insulation because of the problems that it throws up including damp as people here have mentioned.

The house doesn't have cavity wall insulation. We've had a couple of quotes for this but this is for rock wool. In another thread someone mentioned using Urea formaldehyde foams because that's better at air sealing. Is this true? Is using plastic bad?

From what I've read so far, it seems that the most effective way to spend your money is to spend it on insulation. So from this I get that it's worth having cavity wall insulation and external insulation. I'm using the Passivhaus spec as my goal, so I would like to get the U value of the walls down to 0.15. I'm pretty sure cavity wall insulation won't achieve this by itself.

P

PS Also thanks for the links James.
PPS Thanks for your comments Peter. It's nice to know I'm not alone.

Hi James,

Frustration? I don't think so, I am fascinated by the whole thing and feel priviledged to be allowed to participate.

Slightly aggressive? Not from my side, although I am very sorry indeed if you have experienced what I wrote in that way.

I assure you I am not under the impression that building or architecture is simple.

I am aware that people here are building professionals, but I am also aware that this does not appear to permit any practical consensus about how to proceed with this question of green retrofit, beyond the four points mentioned. Internal external or cavity insulation? Breathing walls or not? Passive or active ventilation? cavity walls or not etc.

I am aware that professionals will be able to give an opinion, because I have contacted many of you over the last few years. The problem I am pointing out is that taken together, the advice is contradictory and, as I said, often give with, shall we say 'passion'?
I have experienced great difficulty in having any architect or green builder come to see my house to discuss possibilities, perhaps I just live in the wrong part of the country.

This leaves someone like me in a very awkward position, as a result I have not proceeded with any retrofit so far.

This is not an insignificant problem.

If consensus is not the aim what is? Are you saying that the several million/tens of millions of existing dwellings that require a green do-up will each have to be done by an architect individually?

Peter

Posted By: Peter Clark
including this:

"In general terms, whenever external insulation is being applied to buildings with cavity walls, there is the opportunity to improve the insulation further by filling the cavity. This combination of measures can achieve very low U-values.

Interesting. After the recent discussion we were having where I listed what I'd like to do to any house I buy, I went to the Homes for Good Exhibition last weekend full of enthusiasm to get more information. I had a long discussion about external insulation and cavity wall insulation, and came away disillusioned because I got the impression that this could cause all sorts of damp and condensation problems. I didn't understand the technicalities, but got the impression that a filled cavity can have damp problems and an unfilled one would lose heat.

Now I'm totally confused. It seems that I need to get an expert to look at any house I consider before I buy it, and that everyone I talk to will give me opposing views. So I spend a fortune having places surveyed until I find the right one, then discover that the expert was wrong when his solution doesn't work! Think I'll just continue to live in my van!

If only we had aerogel that's as cheap as rockwool and can be blown into cavities. :o)

Is there demand for a specialist who can survey a building, assess it's thermal properties and produce a plan to bring it up to new standards of insulation and ventilation? What sort of accreditation would they need? Where would you find them if you wanted one?

Posted By: Nick ParsonsFatter insulation. Nick

Thanks Nick,
Of course, but then you are into pantasarus's issue with roof overhang. Also, presumably the external insulation needs to be returned at the window and door reveals? So the windows and doors would be smaller, or major building work? Or could the returns be made of something thinner and more effective?

Presumably in the document I linked to above, they settled for U = 0.24W/m2K to avoid all that.

Of course I can see James's point, every situation is different, but I cannot see how we can proceed as a nation to eco renovate the existing stock without some generally agreed guidelines.

Peter

Peter,

No offence taken.. you caught me at a bad moment....

"If not consensus then what?"

Debate my dear boy..! the heat of the argument... testing one ideas in the furnace of verbal battle... it was good enough for Socrates, Plato and Aristotle..! not of course forgetting the virtue of challenging perceived wisdom in order to push the boundaries of the field....

Seriously, the consensus and "generally agreed guidelines" are there at the basic EST type level, but when you get up to passiv haus there is still little debate about what works... just what works best...

Posted By: Peter Clarkhow we can proceed as a nation to eco renovate the existing stock without some generally agreed guidelines.

The info is there: lots of books, EST guidelines, CAT etc. as a nation I think the way is reasonably clear in general terms...

IMHO this should be a sensible order but subject to lots of variables (see below):

1 - Use less energy by changing bad habits,
2 - fix drafts
3 - extra insulation
a - external if you can because of added thermal mass especially if your house is continuously occupied
b - internally but beware: skirtings/covings, loss of space, thermal bridges and locked in mould
4 - new boiler/tank, use system that can incorporate a range of inputs (thermal store perhaps), if not on a mains gas CH system then see '6'
5 - new windows as good as you can afford
6 - renewable heat and DHW supply
a - solar hot water
b - clean burn (ie smoke free zone friendly) biomass heat source
7 - renewable electricity, wind, PV or water depending on what's most available

Replacing inefficient appliances should filter through this order, from light bulbs at the top to white goods further down depending on the current appliances ages, ...also the house could be extended / reordered with a comparable environmental impact but to provide a more solar thermal efficient occupation pattern...

....but I can see you want the finer details of a specific situation. I suppose what would be nice would be a sort of flow chart, you know the "if yes then"/ "if no then" type thing maybe something for the fundamental section (Nick? Keith?) but for now lets take the points you raise:

The external insulation needs to be returned at the window and door reveals? - YES
So the windows and doors would be smaller, or major building work - NO, AS LONG AS INSULATION IS THINNER THAN FRAME
Or could the returns be made of something thinner and more effective - IF YOU LIKE BUT NOT REALLY NEEDED

With your situation (wanting passiv-haus or close) yes it seems like you'd benefit from a "green architect" or the like for example taking insulation and airtightness to start with all of the following will have an effect and have to be balanced....

-Budget?
-Desired performance?
-Size/type of property - detached / semi / terrace?
-Type of construction
-Aspect - lots of south facing glazing?
-Planning context: strong local visual context / conservation area?
-Acceptable level of disruption?

...and probably some more and that's just for insulation... so all in all if you're serious about it you're gonna have to read the books, visit the experts and possibly pay for advice.... who said it would be easy...? Hope I've helped at least as much as confused...

J

Hi James,

Been on hols, thanks for your reply, I am glad that no offence was taken.

I appreciate that debate is the purpose of the forum, and as I said, I really enjoy listening in and occasionally participating.
Also, I am not attempting to get out of paying for advice, on the contrary, I have a bit of cash to spend on advice, but it is difficult (at least in the North East), to find anyone with expertise, who is interested.
I suppose a flow chart approach might work, I was thinking that, as a result of debate etc, it might be possible to identify some ‘approaches’ – ‘external insulation to such and such a standard, for semi detached or terraces’ for example. Then I could say to my professional help, when I find them, please do that option for me.

On second thoughts, perhaps you need to decide on a philosophy of build first, then find an builder/architect in sympathy. One obvious thing might be either,
‘the techno fix’ – GSHP, whole house ventilation with heat recovery, plastic external insulation etc.
or
‘natural’ – hygroscopic materials, passive ventilation, solid fuel stove, compressed wood external insulation etc,

I know… probably we should do a combination of these… depending on the experienced advice of our retained professional architect.

This thread has certainly helped to firm up some options for me, thanks to everyone.

Peter

Decide on philosophy - great way to attack it

for e.g
- self sufficiency / autonomy, peak oil etc
- harmony with nature
- low energy
- low energy in servicing
- low energy in construction
- low C02 in servicing
- low C02 in construction
- low overal impact LCA

Also of equal importance is something far more boring... ...your budget... you should at least start with a fixed number.

J

Altogether... say after me... ...the first 'R' is reduce...!!!



J

If you have a well insulated house what is wrong with a fridge/freezer as big as you want. The heat coming out of the back is not lost, it stays in the house thus reducing need for other heat sources? Of course it costs but so would alterations to create a larder?
Not so sure many people are so green as to "get rid" of fridge altogether - back to building ice-houses in the garden, with the ice delivered by horse and cart?