thickness of heat sink for ufh

[Jeremy Harris]

38 minutes ago, LA3222 said:

Dodging the question I posed @JSHarris?

 

 

No, just missed your earlier post, that's all.

 

Our package was a fair bit more than just the frame and foundations, as it included all the insulation (slab, walls, roof), UFH in the floor (which was floated smooth enough to directly lay flooring on), guaranteed airtightness of <0.6 ACH @ 50Pa (so internal vapour/airtight layer plus all airtightness taping of joints, around doors and windows etc) and the roof sarking boards, counter battens, membrane and slate battens.  The total cost of this package was £408/m².  Of that cost, the passive slab foundation system was probably about £90 to £100/m², based on other prices I had for passive slabs with UFH installed.

 

P.S:  I'm not peddling anything, either, as I have no commercial interest/connection with anyone.  Our costs are what they are, and seem to be no greater than the costs of other similar builds to me.

[Gone West]

11 hours ago, lizzie said:

@JSHarris I think you will find prices have gone significantly from when you bought yours.  I don't know what size your house is but my frame and slab (without the groundwork prep) alone came in at circa £550sqm plus they could not do the roof so I had to have someone else do the roof trusses which added considerably to the cost of actually getting a shell building (not a watertight one of course). 

 

Then the 3g windows, mvhr, ufh etc all big ticket items for someone who has employ people to do everything, I am not a DIY person as has been shown all too often on this forum LOL.  My core costs are well in excess of yours percentage wise.

 

I am single storey too which is also more expensive to build.

 

It has cost me quite a lot sorting out problems with the whole thing too, it was not a good situation in any way but I am not counting that when I say it is not cheap to build this way.  It may have been a few years ago but not any more. I think it is comparable to brick and block and in some ways may cost more as contractors charge more as there are fewer that do this sort of build whereas brickies are more plentiful if you see what I mean.

I take all these per m2 figures with a pinch of salt. There are so many different ways of calculating the results I doubt whether anyone is comparing apples with apples. If it's a PH compared to a conventional house I would have thought using external floor area more sensible as a lot of the cost is in the floor and walls. Some people use all their costs, some cherry pick and leave out site works or paperwork or whatever. I can come up wildly varying per m2 costs depending on how I work it out. A house costs what it costs and if you've ended up with what you want, that's great. For most people it's the first, and for me the last, self build they will do so there is a steep learning curve and nobody gets it perfect the first time.

[LA3222]

37 minutes ago, JSHarris said:

 

No, just missed your earlier post, that's all.

 

Our package was a fair bit more than just the frame and foundations, as it included all the insulation (slab, walls, roof), UFH in the floor (which was floated smooth enough to directly lay flooring on), guaranteed airtightness of <0.6 ACH @ 50Pa (so internal vapour/airtight layer plus all airtightness taping of joints, around doors and windows etc) and the roof sarking boards, counter battens, membrane and slate battens.  The total cost of this package was £408/m².  Of that cost, the passive slab foundation system was probably about £90 to £100/m², based on other prices I had for passive slabs with UFH installed.

 

P.S:  I'm not peddling anything, either, as I have no commercial interest/connection with anyone.  Our costs are what they are, and seem to be no greater than the costs of other similar builds to me.

I know you have no commercial interest etc, it was just a turn of phrase and not meant to imply anything sinister or ulterior motives.

 

So going off the £408 You mention it would seem that costs have potentially risen by approx 35% since you built which appears to more than can be explained by inflation etc. 

[Jeremy Harris]

6 minutes ago, LA3222 said:

I know you have no commercial interest etc, it was just a turn of phrase and not meant to imply anything sinister or ulterior motives.

 

So going off the £408 You mention it would seem that costs have potentially risen by approx 35% since you built which appears to more than can be explained by inflation etc. 

 

As @PeterStarck mentions above, I'm not sure that prices can be compared that easily from site to site.  In our case we had to do a lot of preparatory ground works on the site anyway, to level it and put in the retaining wall, treatment plant and drainage runs, borehole etc in, so we had already laid the stone sub-base for the house, the slab for the garage and put all the ducts and pipes in where they were supposed to be, with a surveyed and clearly marked out location for the foundation slab, so I'd guess this reduced the amount of work that went into laying it by a fair bit.  I've no idea what impact that had on the cost from MBC though.

 

 

[joe90]

I also agree with @PeterStarck above, my cost was worked out by how much my bank account went down so includes everything.

[LA3222]

I get what @PeterStarck is saying @JSHarris.  I normally would agree it is nigh on impossible to compare, but in this instance where @lizzie first made reference to her costs for just the frame/slab far exceeding your own I think we can compare - it is as they say, apples vs apples.

 

The way you describe your preparatory work is exactly how I would have to do so, therefore it is easy to compare your price vs mine.  As I say, approx 35% increase in price.

 

[Jeremy Harris]

22 minutes ago, LA3222 said:

I get what @PeterStarck is saying @JSHarris.  I normally would agree it is nigh on impossible to compare, but in this instance where @lizzie first made reference to her costs for just the frame/slab far exceeding your own I think we can compare - it is as they say, apples vs apples.

 

The way you describe your preparatory work is exactly how I would have to do so, therefore it is easy to compare your price vs mine.  As I say, approx 35% increase in price.

 

 

I'm not sure that the ground prep was the same for both of us, though, as I chose to do all of the slab sub-base work before MBC arrived on site.  I seem to recall that they normally include this work, including laying ducts and drain runs etc that go under and up through the slab, in their price, as I remember negotiating the first quoted price down initially, because we were doing some of the work.

 

Looking at the ground works chaps cost breakdown, he has listed costs for the house base prep, laying and compacting the passive slab sub-base and supplying and laying the various ducts, drains and pipes under the slab and laying the garage base (MBC just built the garage on the base I'd provided).  Chucking that into the mix increases the price a bit, to around £460/m², but I've no idea how things like differing structural design elements influence the cost.  We don't have any large openings, for example, so their are no steels or large lintels anywhere.

[lizzie]

Guys I think we have hijacked OP topic here.  My observation that the construction type of build a lot of us have (not cheap as we have now established) may or may not be cost effective/heat efficient relative to to OP question of different type of slab/ufh install.  My comments were as to style of build not a particular company.....there are others! Cost of build is a personal matter and we all build to our own pockets/parameters that influences the choices we make on which type of construction method to go for, in quoting my cost per sqm I am not complaining at price (I agreed it!) but commenting that it is not a cheap way to build.  I think the cost benefits are longer term with this type of build and that was what I thought when we decided on it.....hope it works out that way:-)

 

The self build calculator for June 2018 shows TF timber clad to be the most costly way to build......their averages are just that but it comes out more than insulated cavity  brick and block which is at the lower end.

 

I think everyone on this forum knows that my frame and slab were a c**k up and I still live with the consequences of a lop sided frame (no rectification possible) however I have put it to bed, the whole thing made me very ill and I have no wish to go back there.  We have done what we can to mitigate the issues and thats it now. Time to move on.  With the help I have had from all you lovely people I am slowly resolving the issues I still have with various things and now I have finally found someone to sort MVHR and UFH I hope we will be able to get the house functioning as it should.

 

I am learning to love my house after a few years of sheer hell - and I know I am not alone there - I am looking forward to getting my garden sorted this year. 

 

Always  a coffee available for anyone passing who would like to drop in.

[joe90]

14 minutes ago, lizzie said:

I am looking forward to getting my garden sorted this year. 

 

Ha, so am I ?

[lizzie]

@joe90 I may just come and visit for ideas ??

[scottishjohn]

the current trend to go full open plan will not make controlling temp through out the house easy  and I Intend to have rooms and dif zones for temp control 

as I have now  .

why would i want kitchen same temp 24/7 as living area? -separate kitchen keeps smells where you want them .

for that same reason I,m not convinced on MVHR ,as my wife will not stop opening windows to get in fresh air  everyday  ,how ever i build it

Of course we do have fresh clean air up here 

last time i was in a garage with an mot gas analyser in glasgow  and was similar in manchester 

the Oxygen content of the atmosphere was 18 .2 %

here in the country side it is always 20-21%

thats a large difference  that no MVHR will make up for  in your house 

[joe90]

Anyone is more than welcome, just remember to bring your wellies ? (and can you drive a JCB ?)

[lizzie]

7 minutes ago, joe90 said:

Anyone is more than welcome, just remember to bring your wellies ? (and can you drive a JCB ?)

Never driven one but always up for a challenge!!

[joe90]

1 minute ago, scottishjohn said:

why would i want kitchen same temp 24/7 as living area? -separate kitchen keeps smells where you want them .

for that same reason I,m not convinced on MVHR ,as my wife will not stop opening windows to get in fresh air  everyday  ,how ever i build it

 

I only have one zone, downstairs, controlled by room stat in hallway. Stays at 21’ish, upstairs stays slightly less which is comfortable for sleeping (slightly warmer bathrooms with heated towel rails). If we feel chilly in the lounge in the evening (more a reaction to outside weather than reality as it’s never below 20’) we light the woodburner (which we love to see). My wife also loves to open windows but she is finally realising that the MVHR does the same job if not better in the winter as there are no cold draughts.. we also have clean air down here and I think that come the summer I may well switch the MVHR off as we both love to hear the birds with open windows.

[jack]

52 minutes ago, scottishjohn said:

last time i was in a garage with an mot gas analyser in glasgow  and was similar in manchester 

the Oxygen content of the atmosphere was 18 .2 %

here in the country side it is always 20-21%

thats a large difference  that no MVHR will make up for  in your house 

 

Oxygen levels outside are more a function of altitude than country v city. Of course, cities have other components floating around that are less of an issue in the country (although those with certain allergies may disagree!) 

 

MVHR can absolutely make a difference to air quality, especially in relation to CO₂ levels (which affect perceived air freshness far more than the O₂ level).

Re: per room temperatures, I don't zone our downstairs UFH. There's just one thermostat and that controls the whole house. However, you can set up the flow rates per room so that, say, the kitchen is cooler than the living room (or however you like it). Less flexible, sure, but has the big benefit of simplicity, with only a single thermostat and no need for per-loop controls. I haven't bothered, as I'm perfectly happy with it running with all loops wide open.

[ProDave]

1 hour ago, joe90 said:

Anyone is more than welcome, just remember to bring your wellies ? (and can you drive a JCB ?)

Probably but I would need to practice, the levers work "wrong" compared to a 360 digger.

[ProDave]

Re MVHR, you really need to spend some time in a house with it. The air in our house is always fresh. Never felt the need to open a window to "get fresh air" and kitchen smells don't linger and don't spread to other rooms, the mvhr extract vent not far from the hob deals with all of that.

 

Contrary to what many think, it does not recirculate air around the house, it extracts stale air and injects fresh air, exchanging heat from one to the other in the process. 

[Jeremy Harris]

11 minutes ago, jack said:

 

Oxygen levels outside are more a function of altitude than country v city. Of course, cities have other components floating around that are less of an issue in the country (although those with certain allergies may disagree!)

 

 

Interestingly (perhaps...) there's pretty much the same percentage of oxygen in the air at the top of Mt. Everest as there is at sea level, more or less 21%.  What changes with altitude is the oxygen partial pressure, which has  a significant impact on the efficiency of human respiration.

 

The problem is that the affinity of haemoglobin for oxygen is dependent on the partial pressure of oxygen in the air we breathe.  If the partial pressure decreases less oxygen is diffused into our blood.  At sea level, with an air pressure of around 1013mbar the partial pressure of oxygen is about 213mbar, but at, say, 5,000m, the total air pressure will have dropped to around 533mbar and the partial pressure of the same ~21% oxygen level will have dropped down to about 112mbar.  As respiration efficiency varies pretty linearly with the change in partial pressure, at 5,000m our ability to diffuse oxygen out of the air reduces to about 52.6% of that at sea level.

 

The other curious thing (which goes against all the crap you see in films about people suffering from hypoxia) is that there are few outward symptoms.  Your respiration rate doesn't change, as that's controlled by the level of dissolved CO₂ in the blood, so people don't "gasp for air" at all.  What happens to most people is that they just stop functioning properly, may appear intoxicated, visual acuity will be adversely affected and loss of consciousness and death may ensue after a period of time, depending on the persons fitness level, age and the altitude.  I know that I can stay conscious for about 5 or 6 minutes at 25,000ft, but I'm seriously impaired after about 2 minutes, and most probably wouldn't be able to recognise that I was spiralling towards unconsciousness and death after the first couple of minutes.

[jack]

54 minutes ago, JSHarris said:

Interestingly (perhaps...) there's pretty much the same percentage of oxygen in the air at the top of Mt. Everest as there is at sea level, more or less 21%.  What changes with altitude is the oxygen partial pressure, which has  a significant impact on the efficiency of human respiration.

 

Interesting. That's one of those weird double-think moments where I held two opposing pieces of knowledge at the same time without realising the contradiction!

[Jeremy Harris]

Just now, jack said:

 

Interesting. That's one of those weird double-think moments where I held two opposing pieces of knowledge at the same time without realising the contradiction!

 

TBH, I only know about it because it was drummed into my head when I initially did aeromedical training, and then again every two years for a bit over 20 years.  The demonstration of the effect of Dalton's Law of Partial Pressures was by sticking me in a hypobaric chamber every two years and then being told to remove my oxygen mask at 25,000ft.  Tends to ram home the message about hypoxia being very insidious...

[scottishjohn]

2 hours ago, jack said:

 

Oxygen levels outside are more a function of altitude than country v city. Of course, cities have other components floating around that are less of an issue in the country (although those with certain allergies may disagree!) 

 

MVHR can absolutely make a difference to air quality, especially in relation to CO₂ levels (which affect perceived air freshness far more than the O₂ level).

Re: per room temperatures, I don't zone our downstairs UFH. There's just one thermostat and that controls the whole house. However, you can set up the flow rates per room so that, say, the kitchen is cooler than the living room (or however you like it). Less flexible, sure, but has the big benefit of simplicity, with only a single thermostat and no need for per-loop controls. I haven't bothered, as I'm perfectly happy with it running with all loops wide open.

both towns quoted are virtually sea level   as is where i stay 

so it is a direct comparison

[scottishjohn]

2 hours ago, ProDave said:

Re MVHR, you really need to spend some time in a house with it. The air in our house is always fresh. Never felt the need to open a window to "get fresh air" and kitchen smells don't linger and don't spread to other rooms, the mvhr extract vent not far from the hob deals with all of that.

 

Contrary to what many think, it does not recirculate air around the house, it extracts stale air and injects fresh air, exchanging heat from one to the other in the process. 

I understand that --but I know  SHE will still open the windows for a few hours everyday as she has for the last 50 years since she had here own house and i don,t want to be trying to heat the whole county .

I will be allowing for fitting of mvhr in building  design  ,just in case ..maybe even fit the ducts  in tight places 

same as i would always put a draw cord in a ducting --just  in case.makes life so much easier if you alter things later  and costs bugger all to do 

Edited April 15, 2019 by scottishjohn

[joe90]

If my wife opens a window when it’s cold, I switch the heating off and she complains when she gets home as it’s not very warm, “well” I say” if you let the MVHR do the ventilation the house would not get cold! That’s what it’s there for!!,,        Tee hee.

Edited April 15, 2019 by joe90

[Jeremy Harris]

I think I've won the MVHR battle, now, as there was a comment a few weeks ago about how fresh the house seemed.  I just casually mentioned that this was because the windows were closed and the MVHR was doing its thing, and I've noticed since that the outside doors are being kept closed and the latches pulled up to get them to seal, without me having to go around closing them up.  The final observation was this weekend, when a spider was found in the utility room.  I mentioned that they could only get in when a door was opened (they hide under the rain deflector at the base of the back door).  I suspect that the fear of spiders will be the clincher when it comes to keeping the door closed...

[jack]

1 hour ago, scottishjohn said:

both towns quoted are virtually sea level   as is where i stay 

so it is a direct comparison

 

But there isn't going to be a 2-3% difference in oxygen levels between places in the UK. It's more likely to do with machine calibration.