Laying underfloor heating mat, blending height difference out?!

[theanalyst]

Hi guys,

Been searching for answers to my questions and found this excellent forum!
Basically, I'm tiling a kitchen/hallway and downstairs loo.
Same tiles, straight set throughout.

No problem usually, but the customer wants under floor heat mat laid only in the kitchen,
Its a concrete floor and he doesn't want the height differentiation that insulation boards will give.... (Ive told him it will take ages to heat up but it made no odds).
My concern is he is only having the heat mat in the kitchen, so after the tiles continue through the doorway I am worried I will get a height drop of maybe 3-4mm . Just wondering what the best solution is to this?
The only thing I could think of is use some kind of tile joining strip in the doorway, to take out the height difference so I can continue tiling at the 'new' slightly lower level in the hallway!
Any suggestions gratefully appreciated

thanks

 

[theanalyst]

or make the level up with adhesive but I really dont want to have to go that route.!

 

[White Room]

Stand your ground and insist that ufh on a screed floor will be next to useless.

 

[theanalyst]

Thanks whitebeam.
I have tried this! I've basically told him the UFH manufacturer says it has to be laid on insulated boards at least 7mm thick in order for it to work properly.
The guy is a bit zoned in on keeping the levels the same throughout the property....as board and tiles etc would give a 25mm step when the tiling ended on entry to the lounge or dining room.
Basically it was a case of 'well, these other 3 people who quoted could do it how I wanted' (cowboy quotes..) so basically I am just doing as he asked , get paid and that's my job done!

It seems there isn't a good solution to the level issues?

 

[Uheat - Keith]

Make the level up with adhesive.

With a concrete base with no insulation, the project could use our Conservatory range at 200w/m2. Elektra MD200. That would give extra output over the same floor space.

 

[jonnyc]

Make the level up with adhesive.

With a concrete base with no insulation, the project could use our Conservatory range at 200w/m2. Elektra MD200. That would give extra output over the same floor space.

well i am very interested with this post as you are obviously representing u heat and an expert that can guide us.
my understanding is that your 200w/m2 will indeed heat the floor up quicker in a like for like circumstance . ie if the 200 watt mat laid on screed as is 150 watt mat or both on insulation.
first question is . is this more expensive to run than a 150watt mat system.
second question is : if you are suggesting a 200watt mat over screed without an insulation board ,for extra output as you state, what is the calculation that brings you to this statement .
i can only think that the 200watt mat has to heat the sub base below as well because of no insulation board which might increase the the cost of running.
will not the 150 watt mat also do the same job but response time much longer but maybe be cheaper.

 

[Ajax123]

Make the level up with adhesive.

With a concrete base with no insulation, the project could use our Conservatory range at 200w/m2. Elektra MD200. That would give extra output over the same floor space.

What does the w/m2 refer to Keith. Is it the amount of power it uses or the amount of energy it outputs. Reason I so is I am trying to view it against the in screed systems I del with which I generally look for an output of about 60w/m2 in new build... 200w/m2 seems a lot.

 

[theanalyst]

Make the level up with adhesive.

With a concrete base with no insulation, the project could use our Conservatory range at 200w/m2. Elektra MD200. That would give extra output over the same floor space.

Thanks Keith.
That works out well then as I took delivery of 10 metres of the Elektra MD200 bought from Uheat a couple of days ago!


jonnyc - from my research into it, it will cost a bit more to run, but the customer will get improved warm up time from cold which concerns him more than the discrepancy in running cost.
I did advise him it's a lot to spend on materials and labour for a cold floor..!

However I discovered today that the house is a new build, only 12 years old and has some kind of polysterene insulation underneath the top 2" of concrete according to the customer who bought off plan and saw it built. So I am hopeful that we may get a surprisingly good performance compared to what I was initially expecting...
Will post an update

 

[Dan]

You can convert the KW/m2 to BTU's (not sure of the math - I used to know it) and you'd take into account all heat-loss when working out what KW/m2 or BTU's you'd need for a room.

The fact the screed would have no insulation on top of it, would mean you'd need extra KW/m2 as you've got extra heat-loss.

It will cost a bit more to run, but it'll get to the required temperature quicker, therefore switch off quicker once there.

Electric UFH isn't really a replacement for water. Usually it's in rooms that are just being remodelled rather than newbuilds. Newbuilds would clearly want to opt for water.

So the industry standard has been 100 or 150W/m2. For conservatories (which was always assumed would have a higher heat-loss due to there being a lot of windows which are only double-glazed, which doesn't trap heat as good as an insulated wall) they made a 200W/m2 system to counter-balance that.

The screed should always have insulation on top of it. But like in this case, it's not always possible.

So to compensate for the extra heat-loss in a room that isn't a conservatory, you'd simply go for the highest wattage kit you can get. Which is commonly 200W/m2 - I hear some do a 250W now even.

There's no pure calculation for it. It's electric underfloor heating in an existing room. It's not as perfect as water UFH in a brand new room where you can take all sorts into account.

One thing I will say is if it's being used often, I'd never let the screed get to a very cold state, so keep the heating on a very low setting so that it acts a little like a storage heater when it's being used. So you'd turn it up when you're in the room and it'll not need to heat from being fully cold. Not ideal but I've seen many conservatories running their electric UFH like this and it's always been down to floor height and the fact insulation just can't be accounted for.

 

[Uheat - Keith]

Dan #9 above is a great post, he got in before me.

We say 200w/m2 for a Conservatory, 160w/m2 for normal rooms, to cover all ages of buildings.

Some of the quotations we prepare are for houses 100 + years old. Some Conservatories can be from the 1970's.

Remember, with a Digital Programmable Thermostat c/w Air & Floor Sensor, the room will only go to where you want it. i.e. your times & temperature.
A 200w/m2 system will get to 22deg C, quicker than 160w/m2, so both will use approx same amount of electric.
If you have 160w/m2 in an area that has a high heat loss, you may never get it up to the right temperature, so will run on & on.


FYI - Watts to BTU. 1 kw (1000 watts) = 3413 btu's.

Warm regards,