u-values

[RogerS]

Having been in the new place for a fortnight, we've decided that it needs a lot more work doing. First up is to rip off the plasterboard on all the external walls, insert Kingspan between the studs, replace the plasterboard and skim.

We also want to replace the radiators with a more modern style and so need to do heat loss calculations. Most online systems only give a few types of outside wall - brick cavity, brick cavity with insulation, solid brick, timber frame - but none of these fit our type of wall which is probably 200mm stone, maybe a cavity then thermalite blocks. If you look at this picture, you'll see that they paid lip-service to any extra insulation and so our plan is to put Kingspan in between those studs - 100mm thick or thicker if I can squeeze it in.

So my question is does the u-value of this proposal match or come close to any of the u-values used in the online calculators (brick cavity etc) ? I tried Googling but couldn't find any sensible answer. Or at least one that I could understand !

Also not sure but does one need to use foil-backed plasterboard ?



As an aside, the reason why I opened up these panels was to see if there was an original fireplace behind. Up in the loft space there are four original Georgian bedroom fireplaces and it would have been great to find a ground floor one.



My surveyor was round the other day and we investigated a bit more and delighted to find that there is a flue behind those thermalite blocks and so he's planning to come along with a borescope.

 

[RogerS]

I forgot to add that the roof construction is, I think, sublimely elegant and uses a double-fink construction which means that those timbers can be as slender as they are in these photos.

 

[Tusses]

Have you considered insulating on the outside, and letting the walls become a thermal mass ?

 

[TrimTheKing]

Mike will know I have no doubt!

That roof is lovely, unless you want usable loft space! [emoji6]

Cheers
Mark


Sent from my iPhone using Tapatalk Pro

 

[RogerS]

Have you considered insulating on the outside, and letting the walls become a thermal mass ?

Yes. For a nano-second. I think it would be a bit of a shame

 

[Tusses]

:lol: haha .. ok .. I see

 

[AndyP]

Have you considered insulating on the outside, and letting the walls become a thermal mass ?

Yes. For a nano-second. I think it would be a bit of a shame

I thought you had moved up north? What's that blue stuff behind the chimney pots?

 

[RogerS]

Have you considered insulating on the outside, and letting the walls become a thermal mass ?

Yes. For a nano-second. I think it would be a bit of a shame

I thought you had moved up north? What's that blue stuff behind the chimney pots?

I think it's called 'Sky' ...mind you, not seen it for a bit.

 

[Doug]

Mears recommends a 10% increase in calculations for exposed dwellings, so I'd personally base my calculations on 9" solid & not allow the increase.
Also whilst getting the smallest rads which take up the least space to heat up each room is preferable, as long as you use the same criteria for each room ( obviously making adjustments for upstairs & downstairs rooms & room temperatures) the rooms should all heat up at the same rate so when the room stat is satisfied all rooms are up to temperature. This is also presuming you are slightly over compensating which is always preferable due to the base level calculators work from.

 

[RogerS]

Thanks, Doug.

I found a useful calculator on the Celotex site and played around with the values of various types of wall construction. Brick cavity with insulation comes out pretty close, I think, and so I'll run with that.

 

[9fingers]

I would suggest you do your radiator calcs based on a low flow temperature say around 50 C
This will maximise the time the boiler is in condensing mode and so at its most efficient.

Bob

 

[Doug]

Thanks, Doug.

I found a useful calculator on the Celotex site and played around with the values of various types of wall construction. Brick cavity with insulation comes out pretty close, I think, and so I'll run with that.

Makes sense if you are lining with ridged insulation.
Out of interest does the online calculator deduct a % for upstairs rooms? I still use my old dad's rotating disc type calculator which is probably 40+ years old but other than working in imperial & btu's ive always found it accurate.

 

[Doug]

I would suggest you do your radiator calcs based on a low flow temperature say around 50 C
This will maximise the time the boiler is in condensing mode and so at its most efficient.

Bob

Wouldn't that mean increasing the radiator size by 30% though?

 

[9fingers]

I would suggest you do your radiator calcs based on a low flow temperature say around 50 C
This will maximise the time the boiler is in condensing mode and so at its most efficient.

Bob

Wouldn't that mean increasing the radiator size by 30% though?

Yes this is needed to get published efficiencies from modern boilers. I think they specify the performance at return temps around 40C.
Most installations retrofitting a modern boiler on existing systems can't get anywhere hear that.

In the first post Roger is talking of replacing all the radiators which is why I suggested it.

Bob

 

[Phil]

Roger, nice looking house. All stone and no painting.

Did they really paint the walls that colour? :lol:

 

[RogerS]

Yes, I'm afraid that they did, Phil

This u-value nonsense has me in a right kerfuffle.

I've worked out that sticking 100mm Kingsoan in between the existing wall studs is pretty much equivalent in u-value to a brick filled cavity with insulation. So far, so good.

Sticking in the same room dimensions into four or five online calculators for radiator sizes gives me four or five widely differing BTU requirements. From 4800 to 8400 BTU. So much so that I have absolutely NO idea which one to trust.

What makes it even more bizarre is that some of them seem to be using the same calculator engine.

If anyone knows of a definitive calculator then please let me know.

If anyone fancies trying their favourite calculator then I'd be interested to see the results. Parameters are:

length 4.95 m
width 5.56
height 2.8

purpose living room

no. outside walls 2

window area 2.7 sq m wood double glazed

floor - concrete

room above - heated room

 

[old]

Have a look at Stelrad Stars on google then get the app you should find lots of info and be able to design your rad. sizes . it takes time but result is good.

 

[RogerS]

Many thanks, Old. :eusa-clap:

Certainly very detailed !

I put in the parameters for one of the rooms and it came up with a value pretty close to that from one of the other sites which means that I can use that site for the rest as it's a little bit more straightforward.

 

[9fingers]

Making some guesses for parameters not stated, the Myson calculator seems to be coming out at the upper end of your range - about 8000 BThU/hr

http://www.myson.co.uk/useful_services/ ... anager.asp

To be accurate you need air and water temperatures - as suggested in my earlier post to optimise boiler condensation performance.

hth
Bob

 

[RogerS]

.....
To be accurate you need air and water temperatures - as suggested in my earlier post to optimise boiler condensation performance.

hth
Bob

That's a very good point as I recall you mentioning a temperature of 50 degrees to keep a condensing boiler at its optimum working conditions IIRC. Many of these calculators assume, I think, 80 degrees. Therefore presumably one needs a larger radiator for 50 degrees.

Trust SWMBO to choose bloody expensive radiators :evil:

Which reminds me.....time to feed The Beast.

 

[9fingers]

.....
To be accurate you need air and water temperatures - as suggested in my earlier post to optimise boiler condensation performance.

hth
Bob

That's a very good point as I recall you mentioning a temperature of 50 degrees to keep a condensing boiler at its optimum working conditions IIRC. Many of these calculators assume, I think, 80 degrees. Therefore presumably one needs a larger radiator for 50 degrees.

Trust SWMBO to choose bloody expensive radiators :evil:

Which reminds me.....time to feed The Beast.

The Myson calculator allows you to change the mean water temperature. A mean of 55 (flow 60 and return 50) should allow good levels of condensation but the lower temp the better within reason.

Running the boiler at these sort of temperatures is useless for DHW therefore there are a couple of needs of the boiler and its control system.

1) the control system should permit two different settings for the flow temperature.
one should be set low for the radiators and the other set higher at 65-70 for DHW.

2) Ideally the CH should be shut off when heating water for best economy. This not always practical but it is not unreasonable to shut off the CH for say 15mins to heat water (if there is demand) in each hour and you are unlikely to notice any loss of heating comfort.

A further highly desirable feature is to use a weather compensating controller which will estimate/learn the rate of heat loss of the building with differing external temperatures and modulate the boiler power accordingly during CH sessions.

When choosing radiators, it there is not one that is spot on pick the higher output one.

When choosing the boiler avoid the temptation to get one that is too high rated. Whilst having a margin of power in hand might seem desirable, the efficiency will suffer. The efficiency is highest when the boiler is working at or near full output.

Bob

 

[RogerS]

Thanks for the extra info, Bob.

I had a :idea: moment tonight. Sod the calculations. Just get a few electric heaters in a room and turn them on until the temperature is what you want. Stick them on thermostat and wait to see how it develops. Repeat a few times when it's colder outside. Bingo.

 

[Tusses]

if you like sperimenting with stuff like that, then these are fun ....

https://energenie4u.co.uk/catalogue/product/ENER007

 

[Mike G]

..........I found a useful calculator on the Celotex site......

That's exactly where I would have sent you. If you have a wall that varies from the typical, just ring them up and they'll email you a print out of the U value and give you a dew-point calculation/ graph. The good thing about the Celotex site is that they will calculate U values for other types of insulation, not just Celotex.

 

[Jimmy Mack]

I got in a right kerfuffle over u values and clacs. It wasn't until I gave in and just called up kingspan (as Mike suggests) and got them to do the calcs for me.


BTW, that's a beautiful looking house.

Jim


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[RogerS]

BTW, that's a beautiful looking house.

Jim
...

Thank you, Jim. Yes there are a few nice features but and it is a huge and very sad 'but'.

It turns out that the land is totally and utterly water-logged. The local farmer has tried all sorts of types of drainage but to no avail. Our and his locale seems to be a very relatively thin layer of loam sitting on top of rock. So all the rain has nowhere to go and just sits there. And it rains up here. All the bloody time. :evil:

Which means that the dreams of my wife in establishing a most wonderful and beautiful garden have come to a grinding squelching halt. Short of planting willows there is SFA we can do about it and if we could wind the clock back we would never have bought the bloody place.

 

[Rod]

Oh dear Roger that is sad news

Rod

 

[AndyP]

That sounds tough Roger. Is the garden and intended revamp to large for raised beds? They don't have to be square and made from railway sleepers.

 

[Jimmy Mack]

Sorry to hear Roger, I do empathise with that feeling of moving in and finding a catalogue annoyances.

I've was very frustrated with our house after we bought and spent every last penny on it. We live next to a main village road which turns out to be incredibly busy in the mornings from 0500 hrs and within the first couple of months my roadside parked car got written off by a clown...then winter came all the rads and pipes were sludgy and blocked...the boiler was under spec'd and then pooped the bed...the downstairs kitchen has underfloor heating run off a stove which turns out to be expensive and a blind to keep fuelled and not very effective due to the badly designed floor (really thick slabs, bedding, screen ...6"s of thickness above the pipes!). The downstairs is really, really cold (its an 18c Coaching in with thick walls) . Its been dry-lined beautifully and has a lovely a suspended timber floor put in with NO INSULATION or crawl space! The arch to the drive is really narrow to get cars through...the flat roof is knackered and leaks like a sieve...I could go on...but it really, really got me down...(and probably my wife with all my moaning!)...A few years have passed now and I've figured out some of the niggles and I'm slowly working my way through it and begining to like the place (the snazzy man cave at the end of the garden helps).

I don't know if my rambling help in anyway...It does look beautiful and well established on the ground...like Andy, raised beds came to my mind too, certainly easier on the back.

If we can reclaim land from the sea there must be a solution the farmer has not considered. Super Mike will be along in a minute with an solution

Seriously though keep sharing I'm sure we can help or at least cheer you on...it'll be great when you figure it all out - honestly.

Jim

 

[Doug]

You're gonna need raised beds for the peonies Rog & bog gardens are very fashionable, joshing aside I'm sorry to hear of your woes, hopefully things will pick up for you.

Are you anywhere near Berwick on Tweed ?

 

[chataigner]

Pretty much all of the Netherlands is essentally a bog, and they grow some of the best flowers around. There has to be a way.

Sorry to hear you are regretting the move, but until you mentioned some of the problems, most of us I think, me certainly, were envying your fine house.

always look on the bright side of life...

 

[Malc2098]

Don't know what to say, Roger.

Although some may think this contraversial, I can only recount that my first wife and I bought a house back in the early 90s which for a number of reasons she didn't like, in a big way. She became really depressed over it.

Sometimes, however much research and visits you make, there are things you won't find out until after you move in.

If there is something about your new property that one of you just can't live with, then for both of your sakes and health, you just have to cut your losses and find somewhere else, whatever the cost.

Your health is much more important.

 

[old]

I remember Steve Maskery when he was constructing his workshop posting that he did not know how to fix a bent stud .I think he was very tired and i think you could be to, its very stressful moving and sorting out all the essentials to make the place work ,my advice is take a break if you can and have a good think after it .
chris

 

[9fingers]

I remember Steve Maskery when he was constructing his workshop posting that he did not know how to fix a bent stud .I think he was very tired and i think you could be to, its very stressful moving and sorting out all the essentials to make the place work ,my advice is take a break if you can and have a good think after it .
chris

+1

I'm sure there are solutions out there to the drainage problem. The local farmer might have rejected methods as not being appropriate for farming but they might still work for a domestic garden.
Is the area essentially flat? What sort of depth of soil do you have before hitting the rock?

Bob

 

[Mike G]

One of the most beautiful gardens I know is in the Peak District with solid rock just inches below (original) surface level. Or there is the veggie gardens at the CAT in Macchynleth (however the hell you spell it) in North Wales, built on slate (in an old slate quarry). It can be done. It's just much easier if there is any sort of slope, but if there isn't, you'll need to create some sort of sump at a point where the rest of the garden will drain into it. That'll need a digger in with a big hydraulic breaker, but just dig the biggest hole in the rock that you can. This is your pond, and what garden is complete without a pond?

If you can pump the water away from the pond this might also be useful. Build dry stone walls as retaining walls to raise the soil level up above the dampest places. They're great because they don't retain moisture, but they do need to be well "battered back". OK, there is lots of work to achieve the basic structure, and you won't be planting anything much this year, but there is no good reason why you can't win in the end.

As for the house. Dunno. I'd need to have a look. But priorities for me would be to make it weathertight if it isn't. Then to get the windows sorted if they're a problem. Sort the services out, then the kitchen. Then one room at a time. You've got your work cut out, but you can do it!