Ufh loading question

[Nostrum]

Thanks Nostrum, your advice is duly being soaked up. when will architects start giving out heat loss calcs with their plans????:cool3:

Sometimes they will provide the SAP calcs if it's been done.

 

[Sharp Point]

Sometimes they will provide the SAP calcs if it's been done.

Nostrum, can i ask if you know of an easy to use online heat loss calculator? Last year when i did my oftec, we we're set a whole house heat loss calc task and my brain actually split in two. It was only a tester, now if i was taught how to do the if's/ but's and maybe's i would learn.

 

[Nostrum]

Stelrad stars is pretty detailed. Once you get into it it's easy enough although takes a little time. Off plan it normally takes me a couple of hours to model the house.

 

[Chalked]

Nostrum, can i ask if you know of an easy to use online heat loss calculator? Last year when i did my oftec, we we're set a whole house heat loss calc task and my brain actually split in two. It was only a tester, now if i was taught how to do the if's/ but's and maybe's i would learn.

Whole house calcs won't give you an output for ufh, but will give you a boiler loading.
Why don't you send a copy of the plans to a ufh manufacturer ( not speed fit or polypipe) they just say, put pipes at 200 or 100 centres.
Most will give you ( if you buy from them) a installers plan and calculations for boiler load. I bet your builder just uses speedfit and polypipe because his supplier sells it.

 

[Sharp Point]

I

Whole house calcs won't give you an output for ufh, but will give you a boiler loading.
Why don't you send a copy of the plans to a ufh manufacturer ( not speed fit or polypipe) they just say, put pipes at 200 or 100 centres.
Most will give you ( if you buy from them) a installers plan and calculations for boiler load. I bet your builder just uses speedfit and polypipe because his supplier sells it.

Hello chalked, I've just emailed the ufh company. UK underfloor heating in Sheffield and raised the question with their technical guy and he recommended a heat input of 70watts per m2 for a modern new build levels of insulation, but says smaller rooms may require a form of supplementary heat.

 

[Nostrum]

70w/m is current minimum requirements for building regs ie Taylor whimpey standards!

If this is a new build and the property is 800m2 you would think that the cost of the build would lend itself to a higher level of insulation?

 

[Worcester]

Brand new 2015 builds are around 40W/m2, old leakies 100w/m2, 70w/m2 is a good guess, however that is all it is. (We've got one, new build 400m2 house to do, heat load is 12kW)

If like Nostrum and us you live and breath renewables, we have to do full room by room calcs for every job

We find on almost every retrofit property there is is always some cold spot or other, which can easily be supplemented by running a rad off one of the ufh circuits (just its own pair of pipes off the manifold). A GOOD designer / installer will also use a spiral / snail pattern and modify the spacing to heat cold zones ' high heat loss area appropriately (We often close up the spacing alongside patio/bifold door)

Get a copy of this: CIBSE - Domestic Heating - Design Guide 2015 (Domestic Building Services Panel)
and this: CIBSE - Underfloor Heating: Design & Installation (Domestic Building Services Panel) 2012
and this: CIBSE - KS08 How to Design a Heating System
Invaluable

If the guy has spent 7 years getting to this stage, he's not going to be happy if the ufh doesn't work properly. A proper heat loss design is imperative. The stars system will give you a good start.

 

[Sharp Point]

Thanks for your input guys, so really this outfit from Sheffield are just stabbing in the dark? Come to think of it they didn't even ask me for any insulation levels. I must say though, I do install the snail pattern and add more pipes per surface area near' Glassworks'

 

[Sharp Point]

May I add, like I did in a previous post, the insulations are pretty poor....50mm king span floor, 75mm cavity batts in between block/ brick,faced internally with dot n dab plasterboard.

 

[Worcester]

Found this: http://www.eceuk.com/assets/Documents/KS08_How_to_Design_a_Heating_System.pdf