UFH in a Loft Conversion

[paulrockliffe]

I'm about tot start building the new floor in a loft conversion that I'm working through this year. I'm looking at options for UFH at the moment as I don't want to buy/fit anything that causes problems if I go that route wit the heating.

I've tried my best Google skills, but it's a bit of a niche installation, so looking for experience and ideas for the most suitable system for my situation.

The new floor is 145mm joists, sat 14mm clear of the existing ceiling joists. The design has the new floor level running across the top of the bottom chord of the existing King Truss because the easiest build method is if that chord stays where it is, which leaves that 14mm gap.

A between joist setup would be best, but the structure of the floor means there's a strip of joists between steel where there isn't easy pipe access from the side of the room. I've attached a sketchup image that shows the steel running front to back and the steel-flitched king-truss bottom chord, with the joists running between.

I can cover that area by drilling the joists, or the steel, or going under the joists, but I guess the easiest approach depends on what kits are designed to accommodate this situation. Eg, I can't go under the joists if someone doesn't make a shaped link pipe or similar.

I can go over the top of the new floor, but would prefer to avoid adding height and would that need chipboard over the joists, UFH on top of that, then another layer of chipboard?

So, what's the best way to get UFH into this space, what are my options, what should I look at etc?

Thanks!

 

[Ian H]

I think there’s a floor board that’s grooved for the pipes to sit in to keep any height increase to a minimum.

Although having just done a loft conversion, there’s that much insulation in the that I bet it would be warm with no heating.

 

[Leofric]

Why would underfloor heating be the least likely to cause problems?
What is the existing heating system ?
Regards

 

[paulrockliffe]

Why would underfloor heating be the least likely to cause problems?
What is the existing heating system ?
Regards

Because the space needs two radiators and there's only one place to put a radiator that isn't likely to be in the way of *something* when the room is furnished. With it being a loft space, it has under-eaves storage on two sides, stairs on the other, a dormer. So there's not enough flexibility in where furniture can go that I can be sure I won't end up with it just in the way. Especialyl as the use of the room is likely to evolve over time as our kids grow up.

The current setup is a Combi boiler and radiators with more than enough spare capacity to heat the new space.

 

[paulrockliffe]

I think there’s a floor board that’s grooved for the pipes to sit in to keep any height increase to a minimum.

Although having just done a loft conversion, there’s that much insulation in the that I bet it would be warm with no heating.

That's a valid point, given the existing house is uninsulated cavity dating back to 1906 and the new roof will be insulated to modern standards, there is a risk that heating the two floors below to the required temp means too much heat to leak into the ceiling, where it is then trapped. But I can't easily test that theory until it's built and I'd need to be able to easily retro-fit.

Since my first post I've worked out all the stair case dimensions and I have about 60mm of extra build-up I can add before the two steps from landing into the room would be higher than Building Regs allows, so I think it's feasible to delay making a decision until the room is built and insulated and see what the temperature is like over winter if I want. I also have the central heating piping done now, so could add a quick temporary radiator if required. But then we're into the territory if getting it in the neck from the wife.

The other thing I've considered looking into is to use a ducted system to equalise temperatures across all floors (As that would keep the loft cool in the summer and allow me to move heat from my wood burners downstairs around the house and is an easy install) That approach could work with an under-eaves radiator that's boxed in and ducted to pump the loft air through to heat it, but that's a non-standard approach so may be more problematic to get setup so it works well. Would be much cheaper than UFH though.

 

[Ian H]

In ours we put the radiator away from the dormer where the roof comes down to the dwarf wall.

She thinks the room is too hot so the valve is turned down to 3 (out of 5). The rooms 6x4mtrs and the radiator quite small.


Radiator:

Other side of room:

The wardrobe has no radiator and that’s noticeably cooler at the minute.

 

[paulrockliffe]

Yeah, that location would be an option, but I want that space behind to store a couple of mattresses so what will be an upstairs living are can quickly be turned into a guest room, so would prefer not to go that route. The space is about twice the size as yours and that location is too close really to the other place I can put a radiator, so it's not ideal from that point of view either.

I'm leaning towards delaying a decision, but knowing what the options are with UFH would be helpful at this point.

 

[Diyisfun]

Isn't underfloor inefficient heating if its covered with wood (wood is an insulator)?. I have a wet ufh in kitchen/dinner with tiles & its brilliant.

 

[paulrockliffe]

It just takes longer to heat up and cool down really, the wood is an insulator, but the heat has to go somewhere. It will be a bit less efficient because the more heat is retained away from the room, the more will leak sideways, but the sideways area is fairly small with minimal cold-bridging, so it isn't going to be hugely problematic.

As a rough example, the existing first floor central heating has two 22mm pipes running under my bedroom floor. You can find the pipes easily when the heating is on there's such a temperature difference, you notice them walking around. That's the same floor construction, 22mm chipboard, but without proper heat transfer plates etc.