Water underfloor heating - 1970s bungalow, insulation under concrete

[BradR]

Hi, I need some advice on what wet UFH system to get for our renovation of a 1970s 3 bed bungalow. The house had subsidence so in the process of fixing that the floors were dug up and replaced with the following construction: hardcore base, membrane, 150mm insulation, concrete finish. We're left with a 40-50mm gap between the concrete and the base of the front door, which obviously limits what we can do with UFH.

There are of course low-profile retrofit UFH options and we'd have liked to have gone with the Nu-Heat LoPro Max with self levelling compound but that is way too expensive for our budget (double what we want to pay). What are our other options, especially considering our 40-50mm gap, and the 150mm insulation beneath the concrete? I've seen the pre-cut boards that pipes are laid in which have no compound/screed on top, would these work well enough with our floor construction? Or should we go down the normal route with pipes in screed but only have 40mm thickness?

Insulation below a concrete slab means the concrete becomes a part of the thermal mass, so because it has a slow response time would it make sense for the UFH to be run continuously? We'll be installing an air-source heat pump together with insulation above the ceiling and on the outside of the house with a render and/or cladding, so would this help with the response time and/or be sufficient to run continuously or intermittently?

Any help would be really appreciated!

 

[winston1]

Insulation below a concrete slab means the concrete becomes a part of the thermal mass, so because it has a slow response time would it make sense for the UFH to be run continuously?

Very inefficient. Heating a property when there is no one there is wasteful as the losses continue 24/7. Put in a conventional radiator system that you can switch on when needed.

 

[BradR]

Hi Winston, thank you for your reply. If we've improved the insulation of the bungalow then will this improve the response of the underfloor heating?

 

[JohnD]

How many hours a day do you want the house to be cold, as Winston suggests?

A welI insulated house loses heat very slowly.

But if there is, say, a one-hour lag between turning the heat on, and the room being warm; and between turning the heat off, and the room being cold, you simply set the timer accordingly.

The thermal mass means that, in winter, it will never get fully cold.

If you are retired, or have small children, and are at home all day, you may want (some rooms at least) to be heated all day.

 

[Mr Chibs]

Why not reduce the insulation thickness slightly to allow for a thicker screed, then you can use standard fit UFH?

 

[BradR]

Hi John, thank you. The renovation project is actually part of a tv show and we’ll be selling the property after the renovation so we won’t be living in it ourselves.

Mr Chibs, unfortunately the floor has been relaid now with the insulation beneath and this was done prior to us taking over the property. We can’t afford to dig up and redo

 

[Mr Chibs]

Liquid screeds can be laid thinner, 50mm is doable, but more expansive than conventional screed.