One boiler or two?

[dancinplumba]

Only read first bit so far and it's misinformation, Solid walls BLEED heat

 

[dancinplumba]

And contradictory, ie As for the insulation they have replaced the plasterboard by foam back plasterboard



.???

 

[Idealhater]

Thanks Dirksplumbing. I'm afraid double glazing really is a non starter - most of the windows are leaded and with very old glass so there is no way they could be replicated. There are a couple with oak frames and float glass where it might be acceptable to insert double glazed panels but for the most part it would have to be secondary glazing.

Most of the outside walls are lime plastered rather than plasterboarded - this too is covered by the listing.

In our case I think the UFH is OK - it sits on 125 mm Celotex with screed and wooden floor. It's comfortable at 17c whereas the main house needs to be set at 20c for comfort. Partly that's because sitting around in the evening you need more heat but it also reflects the lossy nature of that area.

Just checked this quarters gas bill - £1265!

Sorry - didn't mean to turn this into a double glazing forum.

 

[DirksPlumbing]

Only read first bit so far and it's misinformation, Solid walls BLEED heat

I take you can demonstrate that at a small thermal resistance calculation based on a 3ft solid wall with a small air gap and traditional plaster lathe on one side and around 25mm roughcast outside?

 

[DirksPlumbing]

And contradictory, ie As for the insulation they have replaced the plasterboard by foam back plasterboard



.???

Can you elaborate?

 

[DirksPlumbing]

Thanks Dirksplumbing. I'm afraid double glazing really is a non starter - most of the windows are leaded and with very old glass so there is no way they could be replicated. There are a couple with oak frames and float glass where it might be acceptable to insert double glazed panels but for the most part it would have to be secondary glazing.

Most of the outside walls are lime plastered rather than plasterboarded - this too is covered by the listing.

In our case I think the UFH is OK - it sits on 125 mm Celotex with screed and wooden floor. It's comfortable at 17c whereas the main house needs to be set at 20c for comfort. Partly that's because sitting around in the evening you need more heat but it also reflects the lossy nature of that area.

Just checked this quarters gas bill - £1265!

Sorry - didn't mean to turn this into a double glazing forum.

Well that obviously is answering a few questions.
Lime render is not too bad either.

Having little heatloss in noticeable floor areas and loft insulation leaves at assumed avg. 2.5 ft walls rather radiation losses and to much air exchange.

 

[DirksPlumbing]

Can you roughly tell how many windows and an average size?

Edit: Not for glazing advice, just for heatloss guestimate for the window area.

 

[Idealhater]

I think it's 22 but size varies enormously - smallest 2 x 1.5 ft to biggest 8 x 5ft.

Take the sitting room which is approx 25 x 18ft. It has 1 window 5 x 3, 1 at 6 x 4 and 2 stone mullioned windows each with 4 sections approx 6 x 1.

Every room is different, and in some rooms each window is different not only in size but construction. So nice thought but I don't think you'll get very far. However it's probably fair to say that I'll get a better return from tackling windows than from trying to combine heating systems.

I may not have been clear - the lime plaster is on the internal surface of the outside walls. The exterior is bare Cotswold limestone.

 

[Idealhater]

There was obviously a difference of opinion over heat loss through solid stone walls. I've never been very clear about that - you hear contradictory views. I think it also gets mixed up with the heat store effect of the sheer mass of stone.

I've just found an interesting SPAB ( Society for the Protection of Ancient Buildings ) report from 2011 looking at the U-Values for a variety of traditional wall types. They compared the actual measured value and the calculated value using a "standard tool" ( BuildDesk V3.4 whatever that is ). They found a near linear relationship between thickness and U-Value and also that the calculated U-Value was in most cases much higher than the actual ( 50% or more ). The tool is more accurate with modern standardised construction.

This suggests that walls like mine should be comparable with a modern but uninsulated cavity wall - probably in the 1.2 to 1.6 range. Not great but not as dreadful as you might think.

The windows however are another story.

 

[DirksPlumbing]

There was obviously a difference of opinion over heat loss through solid stone walls. I've never been very clear about that - you hear contradictory views. I think it also gets mixed up with the heat store effect of the sheer mass of stone.

I've just found an interesting SPAB ( Society for the Protection of Ancient Buildings ) report from 2011 looking at the U-Values for a variety of traditional wall types. They compared the actual measured value and the calculated value using a "standard tool" ( BuildDesk V3.4 whatever that is ). They found a near linear relationship between thickness and U-Value and also that the calculated U-Value was in most cases much higher than the actual ( 50% or more ). The tool is more accurate with modern standardised construction.

This suggests that walls like mine should be comparable with a modern but uninsulated cavity wall - probably in the 1.2 to 1.6 range. Not great but not as dreadful as you might think.

The windows however are another story.

I think you are on the right path, just this knowledge is available at least since the 80s. But indeed the high thermal mass suggests to only introduce a slight ripple in the temperatures like on the UFH.
Reason one is the time it takes to lift the temperature in the room including wall surface. Reason two is the fact that a warmer wall gets dryer and therefore increases its thermal resistance.

As I said already, it is important to make sure to place radiators underneath windows where feasible to lift the bottom temperature of the room. Otherwise make sure to be always near the ceiling. Which only works out if your room heights are pretty low.

 

[dancinplumba]

Can you elaborate?

Yes, you say solid walls don't lose heat then say you have insulated plasterboard ? Why ?

 

[DirksPlumbing]

Yes, you say solid walls don't lose heat then say you have insulated plasterboard ? Why ?

Dew point, thermal mass?
And I have not specified it for this house, you may need to talk to the architect about making decisions like that.

But you are aware how to calculate a thermal resistance?
What is better, a reasonable insulating wall or a great insulating wall?

 

[Idealhater]

As the non expert here can I say that I never understood Dirksplumbing to be saying that solid walls don't lose heat - merely that some solid walls lose less that you might think. A 700mm stone wall that is dry and breathing properly is probably reasonable but could be made better by proper insulation. But incompetent insulation could prevent it breathing and make matters worse. I'm now clear that for me getting a reliable boiler and improving my windows is the best investment - my walls are reasonable but will never be great.

On the other hand my son has a Victorian house with a single brick thick extension which was freezing in winter and baking in summer, despite double glazing. Celotex lining and plasterboard has transformed it.

 

[DirksPlumbing]

As the non expert here can I say that I never understood Dirksplumbing to be saying that solid walls don't lose heat - merely that some solid walls lose less that you might think. A 700mm stone wall that is dry and breathing properly is probably reasonable but could be made better by proper insulation. But incompetent insulation could prevent it breathing and make matters worse. I'm now clear that for me getting a reliable boiler and improving my windows is the best investment - my walls are reasonable but will never be great.

On the other hand my son has a Victorian house with a single brick thick extension which was freezing in winter and baking in summer, despite double glazing. Celotex lining and plasterboard has transformed it.

Well I must have expressed myself wrongly then. It was never my intention to say that massive walls do not loose heat. Just the wall thickness has a massive influence on the insulation value.

For example a 3ft massive wall (granite) has a better insulation value than a traditional brick wall with 50mm cavity.
A massive sandstone wall can do that at around 2ft already.

 

[Idealhater]

That's what I thought you meant. You were quite clear but I think dancinpluma misunderstood or disagreed. I'm with you and thanks again for the input.