Hi all,
Just joined the forum today. Moved into an 1800’s detached sandstone house with flat roof rear extension built in 1989 about a year ago. The last year has mostly involved dealing with things like internal damp issues, repairing cast gutters, blocked downpipes, sealing up gaps at windows, reopening blocked under floor vents and a host of other diy jobs, and my main shelling out of cash has been for a mason to repair some of the ashlar stonework cornice and some stone at the front and to rebuild a chimney which was taking in water (one part of the dampness issue, the other part seems to have been mainly internal condensation (sash windows were all painted shut and no vents in bathroom and kitchen).

My next step is to attempt to improve the energy efficiency and trying to decide what to do first. The GCH boiler is a quite old Ideal Mexico Super RS 125, which was allegedly 73% efficient when new, but presumably not now. This boiler is a bit of a workhorse and has lasted around 30 years, but the amount of heat coming out of the flue is criminal!

The other side of things is insulating the fabric of the building. Despite the fact that the old part of the house still has single glazing and no insulation, it seems that it’s the ‘modern’ part that is the weak point. When I got up this morning before turning heating on it was 7 degrees C in the south facing 1980’s extension, but 12 degrees in a North facing room in the original house which has single glazing but had the wooden shutters closed all night. I wandered around the house this afternoon with an IR gun and was getting varying readings from -2 to zero degrees C on the outside walls, but on the double glazing pane around +5 degrees C, and parts of the frame were reading around +8 degrees C. I know that replacing double glazing is not usually the most cost effective thing to do, but this seems to be where most of the heat is leaving the house so I am wondering if I should go there before attempting to insulate walls. I think the issue in the extension is the amount of glass. It’s an L-shape and the sitting area is the bit that juts out, which means 2 out of the 3 outside walls of the sitting area are glass (patio door and windows). My gut feeling is that replacing the old DG windows will have the most impact in terms of comfort, they are old, unusually small gap, and were draughty before I silicone them up.

One concern is that I do intend to insulate the walls eventually and I am concerned that this might be the wrong way around to do things, in terms of insulating the reveals. Is it better to do get the walls insulated first, then get window fitted taking into account any narrowing caused by insulating the reveals. Sorry I don’t know a lot about this so apologies if I am talking nonsense!

Anyway, sorry for the long story, from my look around so far this seems like a good forum with a lot of experienced people so I would really appreciate any comments and pointers.

Cheers
Kenny

Hi gg,
It is built on to the back of the house, with what I presume must have been the original back door connecting the two. Its modern brick construction which has been harled/rendered, with the harling continuing on to the sides of the original house.

I have tried to attach a pic but the site won't let me upload a jpg so will need to figure out how to upload photos.

Kenny

Hello and welcome.

Your image file is probably too big. There's no problem with jpegs. Cut it down to 800x600 or similar.

In terms of what to do first, I'd say the first thing to do is nothing! Take your time. Most people learn an awful lot once they start thinking about a building or renovation project and consequently their idea of what they want to do can change quite a bit. So it's generally best to wait a bit and get an overall plan for everything you intend to do before you start work.

On parts of your house that are rendered, you will quite likely finish up wanting to add external insulation (EWI). If you have parts that have exposed stone or brick that you want to keep then you will have to use internal insulation, which is more tricky, or else use EWI and then put stone or brick slips over it.

Once you've decided what you're going to do with the walls, you could perhaps replace the windows first. By then you'll know what size they need to be and where in the wall you want to mount them (inside vs outside, that is).

Good luck.

Thanks djh. The error said that jpg was not accepted but I have reduced the size and attached.

I believe that I will want external wall insulation, but its complicated by a few factors. Firstly the fact that I won't get planning to do that on the front as I am in a conservation area. I might get planning to do this on the sides as they are already rendered, but this would mean the rendered insulation jutting out 100mm or so and would look fairly odd from the front, so again even if I decided to do this it might fail planning. Finally, one side of the house is right up against the next doors garden, so although the neighbours are very nice and would be fine about getting access, I would be extending my wall by 100mm or so into their property which could be complicated legally as well as potentially being a bit of an imposition on them. Also the side of the extension is butted up against a garden wall so there isnt an even surface for fixing insulation boards.

EWI on the rear wall of the extension shouldn't be a problem though, and there seems to be a decent overhang from the roof as you can see from the picture. My thoughts at the moment are to think about the extension as a separate project from the old part of the house and:

External insulation boards to the rear south facing wall of the extension
The east wall of the extension doesn't matter too much as it is an unheated utility room
An insulated render on the west wall of the extension (effectively actually rendering the old garden wall), combined with some internal insulation on the inside wall.

Regarding the latter part, is there any issue with insulating both the outside and the inside of a wall if you can't get the thickness required from one or other?

I also need to think about the floor at some point but its covered with tiles and I have no idea of the construction below.

Posted By: Kenny_MI am interested in trying to work out the U values for the house based on actual measurements. In the attachment at this link from the states that I found on the web there is a table for this, does anyone know of an equivalent for the UK in C and with U values rather than R, or can point me towards the calculation to work this out.

That's an interesting article, thanks for finding it. I haven't seen a metric equivalent I'm afraid.

Most IR thermometers will read in °F or °C or its an easy conversion if not. The R-value is the reciprocal of the U-value, but its complicated by the different units. There's a lookup table at http://www.myonlinediary.com/index.php/Insulation/US-EuropeanRValueConvertionTables

There are some oddities even in regard to the modern extension that make estimating the U values tricky, for example the main side wall is of unknown thickness, or whether there is a cavity, and is butted up against a historic stone garden wall on one side which must also affect the overall U value.

At some point, you'll probably want to answer questions like this by drilling a small hole to see what's there. Easy enough to fill again afterwards if you don't want a hole.

Gyrogear,
That's not a bad idea, even just to get an idea of the impact of DG or TG. I did something like this last year with the skylights in the same room, although I just taped some bubble wrap in place and after feeling the difference I ordered a couple of DG sealed units and fitted them as a semi permanent improvement the old metal framed/polycarbonate skylights. These made a huge difference which shows that as bad as it is this year its massively improved since putting DG into the base of these two skylights

djh,
I did this a while back using he F deg scale on the IR gun, but I knew that there was something about different units. From what I remember the walls were in on the lower end of the table but I figured at the time that it would only be an estimate anyway, and was just reinforcing the fact that there was no insulation in the wall. I could probably do what you suggest by just opening up where the satellite cable comes in, rather than drilling another hole.

I've had success investigating this sort of thing using a cheap USB endoscope camera connected to a phone.

Posted By: Kenny_MThis presumably means that the temperature of the walls will have reached an equilibrium, while here where we tend to time the heating on and off so perhaps I would need to leave the heating on constant for at least 24 hours to get a more realistic value.

Possibly, although the outside temperature varies throughout the day and night of course. You probably should repeat the measurements on the hour every hour for twenty four hours or something. Easy with an automatic logger, not so much fun with a hand-held thermometer

PS Yes, the 5.678 sounds right.

Posted By: Kenny_MI think I am at the point that I need to start to think about glazing and insulation.

As long as you think about it first and don't just leap into action immediately.

I like the idea of heat pumps, solar etc, but I think I need to be realistic about heating a large old house like this I think that probably means sticking with GCH but going for a modern condensing boiler.

An efficient gas boiler is still a pretty good solution to a lot of problems, so I would certainly keep it as a possibility at this stage.

one of the biggest problems I have found is finding contractors who are actually 'experts'!

its worrying me that I seem to know more about the issues involved that some of the people who are doing it for a living!!

You'll be very lucky to find a tradesman who is more expert than you will become, or even one that agrees with you 100%. That's why it is important to learn enough to be confident of what you want, and to be able to persuade the tradesmen to do what you want.

At the end of the day, it's you that will be paying for whatever is done, and you that will pay to sort out any mistakes. As long as the final result is acceptable to you, that's a good result.

djh/gravelld,
This is actually quite insightful. I've worked most of my life in engineering related jobs and although its not my field I probably understand the principles behind heat transfer better than most double glazing or insulation fitters. I've probably got a tendency to feel that I need to respect the tradesman's expertise but I suppose the expertise a joiner applies in fitting a non standard window is their practical skills, making the window fit well and look good, and its probably unfair to expect them all to also understand the physics behind heat transfer! I think you are right, I probably need to take a Project Management approach to this, decide what I want, research it thoroughly then pay someone to meet my specifications.

There is one question I asked above that I think got buried in amongst all of my waffling. My problem wall in the extension is the west wall as the other side is in the neighbours garden and its unsuitable for EWI because of its irregular surface and the fact that I would be extending into someone elses property. However, on the inside of that particular wall I am short of space for internal insulation. I have been thinking about this for a long time and my current thinking is that if I applied a thinner than normal layer of insulated render on the outside and a thinner than usual insulation layer on the inside wall, I could sum to a reasonable U value for the wall as a whole.

I of course would have to calculate all of this out, but in principle is there any issue with having insulation on the inside and outside of a building wall?

I can't think of any reason there would because all materials in the wall are insulators to varying degrees, but is there something I am not considering here?

Thanks,
Kenny.

Thanks DJH.

Doesn't sound all that different from an engineering project, technicians don't always do what they are asked either, although in some cases the technician knows more than the engineer fresh out of Uni!

Will have to research 'decrement delay' and 'thermal admittance', new ones on me. I suspect this is related to thermal mass or ability to resist rapid changes in temp but will look it up. The wall in question is only about 1/4 or less of the total wall area of the extension so such effects will be limited.

Regards,
Kenny.

Posted By: Kenny_MAs this means that it would probably have to be cavity filled from inside, which would presumably mean pulling off the internal plasterboard

I would expect it to mean that you have to drill a few holes in the plasterboard that can be patched up afterwards, just like injecting from outside, though I'm no expert.

You'd have to calculate the derating of the cables for running inside insulation and decide whether it could cope with the demands of the circuits. Otherwise it would need replacing with a larger cable, or rerouting somewhere else.

If the flat roof felt needs replacing, you can add insulation boards on top of the existing roof deck, before covering them with new 'felt'. Interior ceiling stays untouched. Cut some hatches down through the deck to access the cavity wall while you're at it.

Which direction do the rafters run? If you remove say a 1 foot strip of ceiling and wool alongside the cavity wall, can you reach over to access the cavity? With care this needn't be massively messy.

Think about abandoning the existing cables and blocking their holes through the wall to the cavity. Run new cables chased into the inside face of the wall, or glue on internal insulation boards and run the cable in conduit within that.

We used all the above tricks

Posted By: Kenny_MThe other thing that concerns me is where the draughts are getting into the cavity and I need to figure that out. If its from the roof space then any tied to the roof deck might be a bit redundant. I can't see any vents on the wall so barring the roof I can't see how else it is getting in in such volume.

If there are groundfloor underfloor vents it's possible that they may be allowing air into the cavity somehow.

Thanks Peter, but no vents that are visible.

Thanks djh, this is a good idea, maybe even one of those smoke tablets you use to test chimney flues - although they might need to be lit so not a great idea to through that into the cavity! :)

I'll find something to create smoke and give that a try.