DoUpDiary #20 Specifying a Hanson Jet Floor to curb those heating bills!

Laying a barrow mix concrete floor in a garage

I do hope those trainers weren’t designer!!

After all the mud and mess we’ve got to a point of making things look smooth again, at least in the garage which you can see above, but making the decision caused me a bit of a dilemma. The original specification throughout the extension ( garage, utility and kitchen) was for a solid concrete floor, meaning earth, then stone, vapour barrier, insulation, then concrete. On top of this solid floor we were having underfloor heating then tiles. All good so far.

However…. laying solid floors means knowing exactly where water and services are going and I haven’t as yet decided exactly how I want the kitchen, where all the services you usually find will be, and the utility, where there’ll be a loo, washing machine, tumble dryer and basin. Once a solid floor is laid, the wastes and soil are fixed and concreted in place with no changes possible. Hmmmmm, how to get round this as decision time was looming!

The answer came in an idea mooted by our build team. Bear with me.

The cost of heating the main section of our old Victorian home has always been astronomical, partly due to lack of any insulation and double glazing, but also due to the very high ceilings. With traditional heating systems, whether electric or radiators, the heat works by convection, i.e. rises up and circulates round the room. The problem with this in rooms with high ceilings is that all the heat is at the top whilst you sit still shivering down at floor level, rubbish! Eventually all of the room heats up, but this takes time and more importantly with such high fuel costs now, money. Hence my desire for underfloor heating, not only practical as the consistent low heat rising up from the floor ensures a lovely ambient temperature at human level but also design savvy as there’s no need for radiators on walls. Great for me as I’m taking so many of the pesky things out 😉

Convection heating V Underfloor heating diagram

Underfloor Heating (left) Versus Convection Heating (right)

But, there is a problem. Underfloor heating is usually specified for areas of solid flooring and in our house we have very deep sub-floors, i.e. the distance between the existing timber floor joists and the earth sub-site. In order to get solid floors throughout the existing and original part of the house we’d have had to fill approx 80m2 of 1-2m deep sub-floor area with hardcore, pound it down, then have insulation & concrete – hugely expensive and time consuming. We’re talking thousands of pounds and not a great carbon footprint.

Underfloor heating has been developed which sits in trays between the wooden joists, but you need evenly spaced joists (not always possible in old houses), you need to insulated with rigid insulation between those joists or else heat is lost downwards and it’s not recommended to tile on top as there will still be floor movement so tiles will crack. There are also now UFH systems which are ‘built-in’ to chipboard, but these are designed only for floating timber / laminate flooring to be laid over the top as you can’t screw in from above to secure flooring or you might go through the pipes.

Or another idea – w why not use Pot & Beam floors? This is a system often used in new build as it’s fast, cost effective and gives a suspended yet solid floor, but there’s an issue. It’s great in new builds, with lovely solid walls and foundations to build off but the system is very heavy with it’s precast solid beams and concrete fill panels. Far from ideal in an old house with old bricks and old crumbly walls.

Pot & Beam concrete floors

Pot & Beam concrete floors

Then came a solution connected to Pot & Beam but with a twist. Still using pre-case concrete beams, an innovative alternative is to use dense insulated blocks instead of concrete, far lighter and far easier to use. By building a few internal block walls in the sub-floor to rest the beams on, the result would be a rigid solid floor to rest underfloor heating, screed and tile on.Hanson Jet Floor precast insulated floor at Moregeous Mansions

I’ve decided to use this Jet Floor system in the new extension, allowing me time and flexibility on the kitchen layout and design without increasing costs substantially. Also this means that the floor is already insulated, keeping floor depth to a minimum.

It’s also a deliberation whether we use it in the three main ground floor rooms of the existing part of the house, which would mean:

  1. No need to backfill sub-floors with tonnes and tonnes of hardcore and concrete – costly and environmentally ropey
  2. The creation of an effectively insulated ground floor
  3. Allowing a *solid* floor where a timber one existed before, meaning full (non-tray) underfloor heating
  4. The elimination of radiators at ground floor level, perfect as so many walls are being removed to create open plan areas.
  5. Ultimately lower heating bills and a more toasty living environment!

Hmmmm, decisions decisions.

Keep popping back to find out how we get on with installing them and I’ll report back on how we get on.

As usual Builder Cat oversaw the concrete going down in the garage and ensured a good job was done, soooooo nosey!

Cat and concrete floor

Yep, that’ll do. Next….

5 thoughts on “DoUpDiary #20 Specifying a Hanson Jet Floor to curb those heating bills!

    • The spec insists on 150mm gap and ventilation between the bottom of the beams and the earth over site but hopefully with an 80mm insulated top, plus screed and underfloor heating, we should be nice and toasty 🙂

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