UFH and Screed

BMD

Hi,

I just wanted to get people's opinions on the type and depth of screed to use with UFH. I have read and heard of a lot of contrasting opinions. At the moment I have spec'd for the following;

Downstairs
150 mm insulation (TF70) and UFH in 75mm of sand/cement screed

Upstairs
25 mm insulation (TF70) and UFH in 75mm of sand/cement screed

I feel that downstairs is probably ok as I am reluctant to use easyscreed (30mm) because I have heard it doesn't hold the heat well

I feel that 75mm upstairs may be too much as a quick response time may be more important here and therefore easy screed could be an option.

I would appreciate any thoughts and advice

Gulliver

I put:

100mm insulation + 25mm edge insulation 75mm screed downstairs and
50mm insulation + 25mm edge insulation + 75mm screed upstairs.

The screed has fibre added to it, we've only had one crack which I hear is very good.

As I understand UFH, quick response doesn't come into it. In Ireland, we try and run UFH systems like radiators. I think it works better if it keeps a constant level of heat in the house. If you have a bigger thermal store (75mm) then it should retain more heat in the room. That's the theory anyway. I'll know myself when my heating system is commissioned!

Mike2006

I put 75mm sand/cement Downstairs and 35mm easy screed upstairs.

My reasoning for 35mm upstairs was that you need 19mm over the UFH pipes which are 16mm so 16+19 = 35mm.

I find that the 35mm upstairs allows me to increase/reduce the room temps within 1 hour as opposed to about 12 hours downstairs. This is what I wanted as bedrooms can get uncomfortble when too stuffy so I wanted a 'quick' response time...

Mike.

BMD

Any issues with the easy screed and wet rooms as I have planned for 3 wet rooms upstairs?

BMD

How critical is the 25mm of edge insulation upstairs?

kboc

BMD wrote: »

How critical is the 25mm of edge insulation upstairs?

extremely.

You are trying to prevent the screed from touching anything else. If it does touch anything else then heat will leave your heat source (the screed) and escape to the colder surface. Called cold bridging.