I asked a similar question over in the plumbing forum but no takers on answering this aspect.
I'm looking at using wet UFH in the extended area of our kitchen / family room.
I am concerned about UFH output vs heat loss. There is a lot of glass, plus there is an existing area of the old kitchen, solid floor, which presently has no heating and the ability to get UFH will depend on screed depth and / or difficulty removing solid floor to start again.
Anyway, by my rough heatloss calcs the output assuming 100w/m2 of the "usable floor" area (reduced for kitchen cabinets and margins at wall floor junctions) is marginal in the new floor / extension area stand alone. With the extra heat loss and worst case no underfloor heating in the old area, then there would be a noticeable deficit due to lack of any present solution in there. The 100w/m2 seems best case, not sure if the floor temp limit of 27C for vinyl tiles would step that back as well.
Even putting all that to one side, in the new area stand alone, with it being marginal, it is very sensitive to U values and whether I use the Building regs extension minimums or practical guidance in things like the energy saving trust domestic sizing document. See Below:
E.g. Building Regs U value / Energy saving Trust U value guidance
Walls 0.28 / 0.35
Flat Roof 0.18 / 0.35 (2x)
Floor (with area/perimiter adjust) 0.22 / 0.67 (3x)
Old 1930s Floor - concrete and screed uninsulated EST says 1.09 for age band but seems high compared to other documents even uninsulated?
Windows 2.0 / 1.6 - better to use specific manufacturer U value..
Doors 2.0 / 1.8 - better to use specific manufacturer U value..
Roof being 2x and the floor being 3 times the U value for example are big discrepancies.
I had a look through the SAP document and the floor heat loss with perimiter adjustment is pretty complicated but there are some tables produced which make the EST guidance look a bit overly pessimistic.
Any views on in use as built U values. Are they likely to get close to building regs minimums?
I'm looking at using wet UFH in the extended area of our kitchen / family room.
I am concerned about UFH output vs heat loss. There is a lot of glass, plus there is an existing area of the old kitchen, solid floor, which presently has no heating and the ability to get UFH will depend on screed depth and / or difficulty removing solid floor to start again.
Anyway, by my rough heatloss calcs the output assuming 100w/m2 of the "usable floor" area (reduced for kitchen cabinets and margins at wall floor junctions) is marginal in the new floor / extension area stand alone. With the extra heat loss and worst case no underfloor heating in the old area, then there would be a noticeable deficit due to lack of any present solution in there. The 100w/m2 seems best case, not sure if the floor temp limit of 27C for vinyl tiles would step that back as well.
Even putting all that to one side, in the new area stand alone, with it being marginal, it is very sensitive to U values and whether I use the Building regs extension minimums or practical guidance in things like the energy saving trust domestic sizing document. See Below:
E.g. Building Regs U value / Energy saving Trust U value guidance
Walls 0.28 / 0.35
Flat Roof 0.18 / 0.35 (2x)
Floor (with area/perimiter adjust) 0.22 / 0.67 (3x)
Old 1930s Floor - concrete and screed uninsulated EST says 1.09 for age band but seems high compared to other documents even uninsulated?
Windows 2.0 / 1.6 - better to use specific manufacturer U value..
Doors 2.0 / 1.8 - better to use specific manufacturer U value..
Roof being 2x and the floor being 3 times the U value for example are big discrepancies.
I had a look through the SAP document and the floor heat loss with perimiter adjustment is pretty complicated but there are some tables produced which make the EST guidance look a bit overly pessimistic.
Any views on in use as built U values. Are they likely to get close to building regs minimums?
