First UFH Project

[jimboban]

Hi Guys

 

First post on here - thanks in advance for help and assistance - I am trying to learn quickly, lots left to learn!

 

For the avoidance of doubt, I know enough about general building concepts etc to know that I don't know very much at all - nonetheless I am determined to get to where I need to!

 

I am in the early stages of refurbishing our entire house (6,500 sq. ft) and working on getting all the various components together for the first "room" we are going to work on - and ideally I'm looking to deploy UFH rather than other heating approaches to free up my wall space.

 

I'm reasonably ahead of the game in terms of the basic parameters of the house - we have two shiny new 30kw boilers working in tandem with a header tank - so we have lots of spare "heating capacity" - they barely broke a sweat over the winter -

 

My intention as we refurbish rooms in turn is that I'll run new pipework for everything directly back to the boilers - I don't trust what is currently in the house and if it goes in fresh, I know it's done right.

 

On this level of my ground floor, I have 4 interconnected rooms - my intention is to have everything going back to a single manifold for this level (not necessarily going to UFH the other 3 rooms yet, but need to leave capacity on the manifold for when I do)

 

The first room I am going to work on is going to end up as my kitchen - we've just pulled out everything in the room, so back to a bare screeded floor and walls are back to brickwork etc

 

I have circa 80 sq. mt to cover (yes, I know as it's a kitchen, nothing to go underneath units etc!) - roughly 8 x 10 and almost a perfect rectangle - we're intending to lay slate tiles or similar as a final floor covering

 

The room is currently 240 high - I don't mind if we lose a little height to make doing the floor easier/more cost effective

 

I am thinking we could lay an insulative material over the existing concrete base, run UFH on top of that, then re-screed to finish the floor followed by tiling over that (or maybe even polished concrete instead?) - guessing this will be more effective/cost-effective than some of the overlay approaches I have seen at trade shows?

 

My kitchen design firm have had "an underfloor heating expert" visit to provide a quote - when he was here I got the impression he'd had a previous life selling double glazing - and lo behold, when his quote came in it was about 15k+VAT (which, correct me if I am wrong, is ridiculous for an empty 80sq mt space for just the UFH and manifold?!) (Manifold sized to support the 4 rooms it will end up as, total about 160 sq mt - but quote wasn't to UFH those other 3 rooms!!)

 

Would appreciate any thoughts - I can supply pictures or plans of existing floor plan if that would be useful - any input appreciated (maybe I am going about things totally wrong!) - not entirely sure where to start to get a more realistic quote to do things - desperately trying to find a way to make UFH stack up and at £18k it won't (so I'd be putting radiators back up!!)

 

Thanks in advance

 

Jim

[ProDave]

Hi and welcome to the forum.

 

Your problem is lack of insulation under your present slab.

 

You could lay 100mm of insulation and then your UFH but will you really be happy then with a ceiling height of 2300mm or less?

 

Was your mega expensive quote to dig up the existing screed, excavate a lot, lay new insulation and screed with UFH pipes back at original level?

[jimboban]

2 minutes ago, ProDave said:

Hi and welcome to the forum.

 

Your problem is lack of insulation under your present slab.

 

You could lay 100mm of insulation and then your UFH but will you really be happy then with a ceiling height of 2300mm or less?

 

Was your mega expensive quote to dig up the existing screed, excavate a lot, lay new insulation and screed with UFH pipes back at original level?

Thanks ProDave - quick response much appreciated

 

The "mega-expensive" quote I think was mostly to fund this chaps mortgage for the next couple of months - this is their scope

 

 To supply and fit Underfloor Heating polubutylene Pipe  To supply and fit Conduit for exposed underfloor heating pipe  To supply and fit overlay floor panels with end returns  To supply and fit 12 port steel Manifold  To supply and fit stainless steel manifold UFCH Control Pack  To supply and fit 2 port spring return Zone Valve  To supply and fit 1 x Standard Programmable room stat  To supply and fit single zone master control unit

 

So - I think they're proposing an overlay system, which I guess makes for an easy life - 

 

Our original height was exactly 2400mm - but since then we have removed the existing laminate and underlay - so I imagine we have saved a few mm - but not a full 100... I guess the overlay systems are significantly lower profile?

 

Best

 

Jim

[ProDave]

The problem is if you skimp on insulation, you are heating the earth more than your house. 100mm really is the minimum you should be considering. There are lower profile systems but of course less insulation

 

Have you given any thought to digging up the existing slab to gain more height?

[jimboban]

Thanks Dave

 

To be honest, (possibly for no good reason) my thinking is that I want to try and avoid that if possible (the room, 20 years ago, used to be a swimming pool, the existing floor seems solid, but I dread to think what I might find if I go down...some things possibly best not known!!)

 

I'd come across this (hopefully sharing a link is not bad on here, I am making no recommendation!)

 

https://www.wundatrade.co.uk/shop/home/water-underfloor-heating-kits/wundatherm-tiling-underfloor-heating-kits-filter/80m-wundatherm-ultimate-single-zone-underfloor-kit/

 

Which looks like a low-profile overlay option for about £2k (obviously missing all the electronic bits, labour etc!) - am I in cloud cuckoo land and is this a bad route to take - if I dig out 100mm of flooring, will that be a better approach to take in terms of it actually working?

 

Room is currently very well insulated in general, holds heat well - but getting rid of the rads, and adding stone/slate flooring worries me it might get a bit chilly - hence the UFH needs to work well  I guess efficiency also important due to size of room and not wanting heating £££ to increase massively!!

Thanks

 

Jim

[Onoff]

Can you not dig a test hole to see what's underneath?

 

My bathroom floor  was +60mm compared to the main house. I dug down approx 400mm then built back up.

 

50mm compacted Type 2

Sharp sand blind

25mm EPS

DPM

150mm PIR

Polypipe panels 

UFH

100mm concrete

15mm new tiles

 

= 340mm

[Declan52]

Realistically unless you dig down and put enough insulation in then the ufh won't work as well as you want it to. But as you have said digging all that out it will not only be expensive but the can of worms will be truly opened . You will be digging out maybe at least 250mm to cover enough insulation, some hardcore and dust to get the floor perfectly level then your slab with the ufh pipes in it.

You would be better putting the money into trying to seal the house up so you don't leak as much heat which will mean your house will feel much more comfortable to live in. Any stone floor will feel cold to touch unless your heating is on all the time which will cost a lot of money.

Things like new 2g or 3g Windows and doors, small things like sealing all the holes in your envelope from light switches to plugs to downlights. Then depending on how much renovation you are planning maybe lifting floor boards and sealing up around the joists on the outside walls. Kind of depends how far you are willing to go.

[jimboban]

Thanks guys

 

Paraphrasing, are you saying that an “overlay” type approach is not going to work well? (Without digging up the floor underneath to insulate - which would then make the overlay factor redundant? :-))

 

Do you think perhaps if I use something more modern for flooring (stone effect for example) that would alleviate some of the need to heat constantly?

 

house is pretty well sealed already - the room is question is if anything too warm at present -  whilst I am re-doing the inside, the house was only built in 1975 and seems to be full of insulation everywhere I look!!

 

ive attached some plans for interest - this is the ground floor and I am converted the top right area marked bedroom and bathroom into a kitchen / day room :-)

 

best

 

Jim

[Onoff]

Bloody Hell that's big. Do you refer to the "West Wing" etc?  

 

May I suggest @POTUS if ever you change your username?

 

?

 

I'm sure someone clever here can work out the ££££ heat loss pa through the floor if uninsulated.

 

@oranjeboom on here dug down his whole house and built back up inc UFH. He also did EWI. Check out his blogs here:

 

 

+

 

 

+

 

 

Edited April 22, 2019 by Onoff

[jimboban]

Thanks onoff - it’s certainly a bit of a project (I probably need to start a blog!) - it’s got an interesting history and sat empty for 11 years until I bought it (I need to rename it the money pit!!)

 

my worry is the extra cost of digging it all out / I’m desperately trying to fit the new kitchen into a £100k budget and everything just comes in so bloody expensive... (silly me, originally I was hoping 50k would get me the kitchen done - shows what i know!!) I should probably do a wider thread about “project kitchen” - May be that some clever types on here can find ways for me to do things in a better way!

 

i’ve had 9 builders round now, no one bloody comes back to me - the one guy that did came back asking for over £500k - so I’m resigned to just getting to grips with it myself and getting contractors in to do the actual work - although sadly I have zero experience so it’s a chicken and egg game!! ? (And I am getting so bored of people seeing a nice big house and adding a zero to their quote!)

 

thanks to all for input so far ?

[Onoff]

3 minutes ago, jimboban said:

I need to rename it the money pit!

 

Sorry, that's taken! ?

 

@MarkyP's comments on EWI very informative too if you go that route:

 

 

[Onoff]

I'd urge you if you can to visit a completed passive / exceeding passive spec house with super high air tightness and marvel and the draught free feel and quietness. I visited @PeterStarck's and it's beyond impressive. Interestingly he doesn't have UFH but the whole place sits on 300mm of high performance eps under the slab (as in fact do many here that also incorporate UFH). Really it'll change your way of thinking.....and make you regret not having knocked down and rebuilt! ?

[Simplysimon]

14 minutes ago, jimboban said:

I should probably do a wider thread about “project kitchen” - May be that some clever types on here can find ways for me to do things in a better way!

https://www.usedkitchenexchange.co.uk/

https://www.theusedkitchencompany.com/

https://www.kitchenexchange.co.uk/

 

[jimboban]

Thanks Simon - that was a real eye opener hadn’t even realised such sites existed! (Not for me but very interesting)

 

I’ll start a thread about the kitchen somewhere more relevant ?

 

For now, I think you gents are kindly telling me the “overlay” approach is crap ? (?) - will get back to my drawing board!!

[Onoff]

43 minutes ago, jimboban said:

For now, I think you gents are kindly telling me the “overlay” approach is crap ? (?) - will get back to my drawing board!!

 

It'll work but you'll be haemorrhaging money on fuel. Spend on airtightness and insulation. YOU ONLY PAY FOR INSULATION ONCE!

 

Are you considering MVHR? 

 

Just the feeling your boilers are working overtime. 

 

Trades will take your money all day long. You can't do the room at a time approach?

 

I've done our bathroom as a bit of a retreat from the shithole that is the rest of the house. Next on the list is the room most central to the house where I'll site the UFH manifold and run ducts off to all the other ground floor rooms. As I redo those floors the UFH pipes can go in.

 

Can't think of as big a floor area as yours... @AliG maybe, and he's got an indoor pool within the thermal envelope! Be interesting to compare heating bills.

 

I think @PeterStarck's space heating requirements are <1.5kW per day...or is that DHW?

 

 

Edited April 22, 2019 by Onoff

[PeterW]

@jimboban overlay will work but not as a direct heat source unless you want to spend a lot on heating ..! 

 

If you got another 25mm insulation under the floor then you may be making a tiny dint in the issue ... problem is that stone floors like solid surfaces so you need to add something like Fermacell floor over the top so you’re looking at losing 60-70mm overall. Are you set on a stone surface ..?

[Onoff]

If you raise the floor heights then you'll need to redo all your doorways too!

[newhome]

1 hour ago, jimboban said:

it’s got an interesting history and sat empty for 11 years until I bought it (I need to rename it the money pit!!)

 

 

I assume you have been living in the house since you bought it? It’s a pity you didn’t start the work before you moved in as you can reclaim all the VAT for renovating a property that has been empty for 10 years. As soon as it’s occupied if you haven’t started the work then you can’t. That would have been a 20% saving from the get go. 

[Ferdinand]

Welcome @jimboban.

 

I can see that this is going to be a party thread.

 

However, one initial question ... your house was built in 1975. 

 

Are you absolutely sure that there is no asbestos in it? That is nearly peak usage time.

 

Several of us here have lost parents or partners to related diseases.

 

Ferdinand

 

[Ferdinand]

14 hours ago, jimboban said:

First post on here - thanks in advance for help and assistance - I am trying to learn quickly, lots left to learn!

 

?

 

Quote

Room is currently very well insulated in general,

 

On insulation. Do you have any details on what you have actually got? Material, thickness, u-value etc.

 

The space that insulation takes up when it is in a pile is quite startling. Assuming yours is a house not a bungalow, I make your wall, roof and floor area about 1300sqm. All those surfaces insulated with 250mm of EPS (OK, but worse performance than many here would use) would require 4 x 40ft containers, or a volume stacked solid equivalent to your 10 x 8  x 2.4m kitchen. Plus a third.

 

Quote

our entire house (6,500 sq. ft) 

 

As it happens my parents restored a 5000sqft house that had been empty for several years. That was a small manor of 5000 sqft. They took two decades and did it slowly. Everything always costs that much more money or time if there is that much of it. By the mid noughties their energy bills without a strategic 5 year fix would have been running at 6-7k per year.

 

Quote

 fit the new kitchen into a £100k budget

 

I thought when I first read it that that was the house budget !

 

On insulation and slabs, have you considered external wall insulation? It may be a bit daunting as you would be looking at spending 80-100k on it, but if you are looking at all that digging for ufh, the EWI plus extending it downwards by 600 or 900 may well be a viable option. Needs analysis, but if you save 5-6k a year on bills it could be viable.

 

You need to do some heat modelling including long term costs.

 

My experience on multiple attempts to consider EWI on houses roughly 10-20% of that size is that it is usually totally unviable if you have done much other stuff first. But here if you get to avoid some major work, who knows?

 

Ferdinand

 

Edited April 23, 2019 by Ferdinand

[Gone West]

8 hours ago, Onoff said:

I think @PeterStarck's space heating requirements are <1.5kW per day...or is that DHW?

IIRC it's 1.1kW for space heating when it's very cold outside, but it's not a large house. I don't know what I use for DHW.

[Jeremy Harris]

If it helps, the this spreadsheet will estimate UFH performance and give the approximate heat loss: Floor heat loss and UFH calculator.xls

 

UFH is always less efficient than radiators, as there will always be heat lost downwards into the underlying ground, or air space with a suspended floor, but adding insulation can reduce the heat losses a lot.  We have 300mm of EPS under our floor, and that reduces the UFH heat loss to around 8.5% (so for every £100 we spend on heating, around £8.50 is wasted through the floor).  If we had no insulation at all under the floor, then the losses would be a great deal higher

[AliG]

I saw my name mentioned. At work, so this answer may be a bit rushed.

 

I actually have more experience in this from our last house where we took up the floor and installed UFH. That was on a much smaller room, around 35 square metres.

 

Experience of that would suggest it is not a good idea with the caveat that we had a suspended timber floor. They put 100mm of PIR between the joists and then heat spreader plates above the joists. This was then covered with ply and tiled, so we had around a 50mm step up into the kitchen. this was OK, but my OCDness hated it.

 

UFH is designed for much lower temperatures and output than radiators. However, it simply could not output enough heat at the normal running temperature of UFH. I had to up the flow to around 60C and even then it wasn't always enough on the coldest of days. Partly this was due to the kitchen installers leaving a few badly filled holes behind the units when they took out the old kitchen which didn't help, but the radiators worked fine compared to the UFH.

 

To test this you can calculate the heat output of your current radiators. It is difficult to get more than 100W/square metre out of UFH, the floor will get too hot. So the maximum output you are likely to get is around 6kw allowing for units  etc. This is roughly the output of 4 large radiators. 600x1200mm

 

I believe that a floor has to have a minimum U-value for BC to sign off on UFH. I think you need around 100mm of PIR. If you can dig down and get this in and end up with a solid screeded floor then it could work well. Many of our issues were caused by the suspended floor. It flexed and tiles popped and cracked. I think this may also have been affected by the high flow temperature required. I think UFH also requires the "thermal mass" of the floor to act as a large radiator constantly putting out heat. Our system was particularly poor at coping with large external temperature variations.

 

Basically UFH is a system for a well insulated house with modest temperature variation across the day. I would try and consider what you are doing with the whole house at once, insualtion, new windows etc rather than room bu room.

 

BTW £15000 is crazy. My cost was £5400 including a few hundred to connect it to already installed UFH in another room and a few hundred to connect it to the boiler. This included taking up the old floor and installing PIR as well as spreader plates and the new floor on top. Unless there is a lot of building work your job should easily be doable for under £100k. 

As to heating requirements, we only have one 40kw boiler for the house and pool, a total area of around 10k square feet. I have onyl just finished getting everything sealed up and am trying to get a handle on running costs. I estimate around £500 a year for DHW, £500 a year for the pool and £1000-1500 a year for heating. Heating is running at aorund 2x what @JSHarris heat loss calculator said due to insulation not working as well in practice as in theory due to construction issues. This total is around what we spent on our last house at 4500 square feet, the heating costs is probably less. I am guessing with 2 boilers you are coming in more in the £4000-5000 range.

 

[Mr Punter]

If you are able to rule out UFH and tiles, you could get some insulation on top of the floor, then finish it with an overlay board and LVT (Amtico, Karndean etc) and heat with radiators.

 

If you can live with the floor being 60mm higher, you could use 40mm thick pir type insulation (Kingspan, Celotex, Xtratherm etc) at a cost of about £7/m2, but the insulation improvement will be OK but not great.  The fitting, overlay boards and finishes will likely bring the cost up to £70/m2.

 

If you are feeling flush, you could use Kingspan Optim-R 40mm thick which will be four times better at insulating but will cost an extra £130/m2 or so.

[ProDave]

2 hours ago, AliG said:

hey put 100mm of PIR between the joists and then heat spreader plates above the joists. This was then covered with ply and tiled, 

 

UFH is designed for much lower temperatures and output than radiators. However, it simply could not output enough heat at the normal running temperature of UFH. I had to up the flow to around 60C and even then it wasn't always enough on the coldest of days.

This mirrors my findings the spreader plates are not very effective.

 

Downstairs we have UFH using a biscuit mix as the heat spreader and it works very well.

 

Upstairs we have UFH with spreader plates under the chipboard floor, then tiles.  It works to take the chill off the tiles but is next to useless at actually heating the rooms.