Dazza

Thanks again guys. Yes, I def need to draw out a plan for runs! So it is definite that I need a system boiler with hot water cylinder - think someone suggested a 400 litre unvented or thereabouts (as well as kitchen etc will have 4 ensuite bedrrooms with showers)? Sorry if this sounds like a silly question, but how do you maintain pressure if all 4 showers were running at the same time? Also, the location where water tank would go is a bit limited in head height so I cannot have a "tall" tank - does anyone have any recommendations for tanks to suit (preferably pre plumbed to make life easier for me!). Also, is there a general consensus of a good brand boiler to go for or is that one of those where everyone has a different opinion? I did get a recommendation form an online boiler supplier for a Viessman boiler - any thoughts?

Thanks again guys, you have been most helpful!

Well, I would be foolish to ignore everyones advise, so I will stay away from multifoil! Actually the celotex with plastboard over was not that much more expensive and is tried and proven. Of course if I could get insulated plasterboard at a good price, then that of course is the easiest option.

Thanks for the reply - I take it you have experience with the multifoil? Surely it must work or wouldnt pass building control?? Looking at Kingspan they specified fitting the insulation on 25mm battens too rather than direct bonding to wall, so it seemed to me that was the best option and also gave a service void which is very useful. Excuse my ignorance, but who is CCF?

Yes LPG is more expensive but cleaner and can be hidden away - we went with LPG with our eyes open because it suited our needs better. I think it is also getting more competitive - we are with flogas and is £0.40 per litre + VAT and contract was only 2 years - we also took out the contract about 1 year ago and only just got around to installing the tank and getting filled, so will last us until we are out of contract anyway!

Thanks for all the replies!! It has been really useful and productive to get others input! So, I have had a real rough look at approx energy loss and cost of internal insulation does definitely seem worthwhile! Just in case anyone is interested I approached it like this - the U value for my solid brick walls is probably somewhere around 2 W/m2.K - I have assumed this for the roof too as that is uninsulated. In my area I have figured the average annual temp is around 10C, so with an internal temp of 20C, give my walls a loss of 20W/m2= 175kWh/pa. Ignoring doors and windows, I have roughly calculated total area of external walls and roof is 655m2 So assuming gas is around 7p/kWh, annual cost would be £8146 for heat loss. If I insulated to U value of 0.3 this would come down to around 3W/m2.K loss per m2 = 26.28kWh/pa = approx £1205 pa cost for heat loss. So insulating to achieve 0.3 could reduce annual cost by around £6900!! On rough costings, I figured to insulate 655m2 using Kingspan K18 it would cost £14410, using 50mm Celotex and plasterboard over would cost £7,618, or using multifoil it would cost approx £6340. So it seems to me a pretty convincing argument that the insulation will pay for itself pretty quickly! Which brings me to my next question - the multifoil looks like the cheapest option and it is lot easier to work with than PIR boards, so was thinking of going down that route. Does anyone have any experience using multifoil for internal wall insulation?? As we have decided that internal insulation is the way to go (it will actually help with the refurb as well for ease of wiring etc) then once insulated, I think the boiler demands will not be anywhere as large so can get away with a single boiler.

LOL! Actually I exaggerated - the flow and return pipes from the boiler are around 60-70mm OD, but when covered in lagging look much bigger!

Thanks for all the replies and advice guys. We are definitely going with the LPG (obviously as it is installed!), but I guess now it is a matter of what size boiler we require etc. The property is old and has triple brick walls (so over 300mm thick) but does have double glazing - there is also no insulation between floors. As has been suggested, it does seem like a good idea to get an idea of the heat losses from the property, so Im going to go away and work on that. Can anyone suggest a good place to find U values for the various elements - external walls/internal walls floor etc?

For a variety of reasons we wanted to move away from oil, hence we went to LPG. We did the numbers on it and actually it worked out pretty close as a cost comparison - but we also got the in ground tank tank supplied and fitted FOC!

Thanks for the spreadsheet - I will give it a go and then we can see where we are. I was reticent to insulate the house as it is quite large and to insulate all the walls floors/ceiling will cause a lot of disruption and cos, but I will have a go at the spreadsheet and see what I find.

I can get the tank vertically within about 2m, but horizontally it would be about 10m. Reason for removing the pipe work is that want to use the area where it is currently as a habitable space and the pipe work goes everywhere in the basement making it pretty unusable at the moment. There some even bigger pipework - some of the pipe work is about 4"!! So I guess for the heating, I would need to get all the bigger stuff out and bring it down to 15mm which might be achievable?

Havent done heat loss calcs but will give it a go - yes it heats the 150L HW cylinder easily!

Thanks for the reply. The current hot water tank is a vented 150l tank just behind and to the right of the boiler - although it leaks a bit and needs replacing. The current boiler is in a cellar, but the replacement cannot be in a cellar as it is gas, so new gas boiler will be on ground floor. I was hoping to get away with a combi because it makes installation so much simpler, but it seems that is not likely. If I have to have a HW tank it does add a lot more complexity as I was hoping to be able to effectively bypass all the current installation and allow me time to rip it all out, but if I had to add a new HW cylinder with new boiler I would probably need to instal it temporarily and then move it later - but if thats what I need to do, then so be it. Thanks for the advice on the maglclean thing - never heard of them - will look into it! At least that will save me some hassle up front and allow me the time to gradually replace the pipework as I work through the place!

Looks worse than it is - you are thinking asbestos? It is actually yellow rockwool insulation type stuff.