Advice on spec for heating system: Extension + UFH + Oil system

25 Jun 2010
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United Kingdom

We currently have an old (circa 10 years I'd say) oil fired boiler (situated in the kitchen) and gravity fed (I think) heating system (cold water tank in the loft, hot cylinder in airing cupboard on landing). Standard old rads (some single/some double) in our 4 bed house.

We're planning an extension which will involve creating a large open plan kitchen/dinner/living area with lots of glass aspects (most on the existing footprint but a small part on new extension) and converting part of the old downstairs space to an annex. The house was originally an old cottage but has had multiple extensions added in the last 20-30 years. It has double glazing throughout and appears reasonably well insulated - clearly we'll be trying to up spec this as much as possible when doing the renovations.

I would like to install wet under floor heating at least in the open plan area and if feasible in the remaining downstairs spaces (annex, loo, hallway, utility, snug/living room). Given that 90% of it would be laid on the existing concrete slab we're probably looking at a retrofit low profile solution such as Nu-Heat Lo Pro or similar.

There will be minimal work done upstairs (one new bedroom, redo existing bathrooms) so that will likely remain on radiators rather than UFH.

As part of the work we'd like to take the opportunity to move the boiler outside (possibly under a porch area). We live in the sticks so moving off oil isn't an option.

Here are a few questions I have:

- Anyone got any experiences of retrofitting UFH to existing slabs (potentially un-insulated)?

- What type of boiler would be best in this situation (regular, condensing, combi etc)? Any go to brands?

- Given we would be redoing x2 upstairs bathrooms would it be simple/feasible to install the wet UFH in those two rooms upstairs too? (I know the wife would be v happy if we had UFH in the bathrooms!)

- We're in a hard water area. Given the small UFH pipes is it best to have the water softened before entering the system (we currently have a softener in the house).

Is there any other advice/things we should consider?
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