Ren­o­va­tion Clinic:

Our ex­perts an­swer your need-to-know heat­ing ques­tions, from boiler woes to up­dat­ing heat­ing sys­tems and retrofitting un­der­floor heat­ing and more

Homebuilding & Renovating - - CONTENTS -

Your Heat­ing Ques­tions An­swered

QWe’ve re­cently bought a home to ren­o­vate and we had hoped to keep the ex­ist­ing boiler as it’s rel­a­tively new. How­ever, the hot wa­ter never stays at the right tem­per­a­ture for very long. Is the boiler the wrong size for the house per­haps?

ATIm Pullen sAys: If the boiler is too small it would be run­ning for much longer than might be ex­pected, which would be fairly ob­vi­ous. And, it might never reach the de­sired tem­per­a­ture in the first in­stance.

You sug­gest that the wa­ter ‘never stays at the right tem­per­a­ture for very long’, and pre­sum­ing there is a hot wa­ter cylin­der, the im­pli­ca­tion is that the wa­ter does get to the right tem­per­a­ture, but is then used up. There­fore the cylin­der size would be the first thing to look at. If it’s too small for the do­mes­tic hot wa­ter and space heat­ing re­quired by the house­hold, it would cause this ef­fect. It may be poorly

in­su­lated, which again would have a sim­i­lar ef­fect. “The old cop­per cylin­ders were very in­ef­fi­cient, never large enough, with small pri­mary coils (which gives a slow re-heat time), and bad in­su­la­tion caus­ing the cylin­der to lose heat very quickly,” con­firms heat­ing spe­cial­ist Brent Wither­spoon of Chelmer Heat­ing. In ei­ther case it would take a while for the boiler to catch up with de­mand.

An­other pos­si­bil­ity is the wa­ter con­sump­tion. Power show­ers, hav­ing more baths, and even hav­ing more peo­ple in the house, can use a great deal more hot wa­ter than the sys­tem was de­signed for and that could cause this ef­fect. The so­lu­tion would again be a big­ger hot wa­ter cylin­der.

With the in­for­ma­tion avail­able it is re­ally dif­fi­cult to give a de­fin­i­tive an­swer. The best ad­vice is to get a com­pe­tent plumber in to check the sys­tem out. It is prob­a­bly not the boiler, and that needs to be con­firmed, but it could be the boiler set-up and/or the hot wa­ter cylin­der. QWe’re hop­ing to re­place the ra­di­a­tors in our home with un­der­floor heat­ing. How dis­rup­tive will the work be?

ATIm Pullen sAys: It is al­ways go­ing to be dis­rup­tive. There are two op­tions: con­ven­tional un­der­floor (UFH) which would be 40mm to 75mm thick and would go be­low the ex­ist­ing floor, mean­ing ei­ther ex­ca­vat­ing a con­crete floor or lift­ing floor­boards. The sec­ond op­tion is a low-pro­file UFH sys­tem, like the NuHeat Lo-Pro sys­tem; these sys­tems are less than 20mm thick and sit on top of the ex­ist­ing floor.

Low-pro­file sys­tems gen­er­ally al­low you to deal with one room at a time, while con­ven­tional sys­tems gen­er­ally re­quire the whole floor – through­out the house – to be dealt with at the same time. This is be­cause con­ven­tional sys­tems re­quire a screed, be that ei­ther flow-screed

(which is the 40mm one) or a sand and ce­ment screed (which is the 75mm one). In ad­di­tion, the UFH pipework to each room or zone needs to be taken to a cen­tral man­i­fold, and then con­nected to the hot wa­ter cylin­der. There needs to be ca­bling for con­trol sys­tems in­stalled and the pipework to the ex­ist­ing ra­di­a­tors taken out.

The low-pro­file sys­tems are de­signed specif­i­cally for retro­fit sit­u­a­tions but as a stand­alone project there is still a lot of work to do and that can only up­set the happy run­ning of the house. Hav­ing said that, UFH does in­crease com­fort, re­duce run­ning costs and open up more floor space. The ad­vice would be to get two or three po­ten­tial sup­pli­ers in and talk through ex­actly what has to hap­pen. This will give you a bet­ter idea of the ex­tent of the dis­rup­tion and how long it is likely to last (bear in mind that it will al­ways take longer than you are be­ing told).

Q We want to re­place our elec­tric stor­age heaters with ra­di­a­tors and up­date our heat­ing sys­tem. Where do we start, what’s in­volved, and how much will it cost?

A David Hil­ton says: As you have elec­tric stor­age heaters you will have no pipework or ra­di­a­tors. Let’s as­sume you want to in­stall a gas­fired cen­tral heat­ing sys­tem. First you will need to get the gas con­nected. A cal­cu­la­tion will be done to de­ter­mine the size of the me­ter re­quired based on your max­i­mum de­mand; the util­ity com­pany will then pro­vide a quote to in­stall a pipe and me­ter.

The next de­ci­sion will be whether to opt for a sys­tem boiler (with a hot wa­ter cylin­der) or a com­bi­na­tion (‘combi’) sys­tem that pro­duces in­stant hot wa­ter and has no hot wa­ter store. If you have more than one bath­room it’s prob­a­bly best to go for a sys­tem boiler. You will then need to plan where the pipes will run (ei­ther chased into a wall or boxed in within some form of sur­face-mounted trunk­ing), as well as where the boiler and hot wa­ter cylin­der (if you have one) will be in­stalled.

The ra­di­a­tors can ei­ther be in­stalled in a tra­di­tional par­al­lel sys­tem, or to a man­i­fold with sep­a­rate pipes to each ra­di­a­tor. New boiler in­stal­la­tions also need to com­ply with Boiler Plus reg­u­la­tions, mean­ing you will need some form of con­trol for the boiler. As you are putting in a new sys­tem you can choose whether you want a wired or wire­less con­trol. Man­i­folds are eas­ier to con­trol as all the wires to the valves are in the same place, but you still need to have ther­mostats in the room. Al­ter­na­tively, wire­less sys­tems can be in­stalled that have bat­tery-pow­ered ther­mostats and you also have the op­tion of bat­tery-pow­ered ra­di­a­tor valves for par­al­lel ra­di­a­tors.

The cost of retrofitting a cen­tral heat­ing sys­tem will de­pend on the scale of the project. A sys­tem boiler will cost around £700-£1,000, and a com­bi­na­tion boiler will cost £900-£1,400. The in­stal­la­tion of the boiler is around £1,500. A hot wa­ter cylin­der will add around £700-£1,000 plus in­stal­la­tion, which could also be up to £1,000 de­pend­ing on ma­te­ri­als and pipe runs. In­stalling ra­di­a­tors will cost around £500 per ra­di­a­tor as a generic es­ti­mate, but it is dif­fi­cult to as­sume the pipe lengths and in­stal­la­tion com­plex­ity. The con­trols may also cost around £100 per room.

If you are off mains, then an oil boiler would cost around £1,200 to £2,000, or an air source heat pump will be around £10,000 to £15,000, but you may be el­i­gi­ble for in­cen­tives that pay back a large per­cent­age of the in­stal­la­tion costs. Q We’re cre­at­ing a new util­ity by con­vert­ing one of the smaller rooms ad­ja­cent to the kitchen, and would like to in­stall an elec­tric un­der­floor heat­ing sys­tem here. What are our op­tions?

A dAvId Hil­ton says:

You can quite safely fit elec­tric un­der­floor heat­ing (UFH) to an ex­ist­ing floor but there may be an up-lift in the floor level, which could re­sult in un­even thresh­olds. The ideal sce­nario is to ex­ca­vate the floor and in­stall some in­su­la­tion (to re­duce con­duc­tive heat loss) fol­lowed by a heat-re­sis­tant back­ing board or screed, be­fore lay­ing elec­tric UFH. This is not al­ways pos­si­ble, and there­fore it is worth shop­ping around as there are a num­ber of dif­fer­ent prod­ucts that are aimed at dif­fer­ent in­stal­la­tion pro­files.

The thinnest sys­tem (best­suited to tiled sur­faces) has wires at­tached to a thin mesh and the whole prod­uct is less than 2mm thick. The floor lev­els are not raised as the tile ad­he­sive is ap­plied di­rectly onto the mesh and the heater then ef­fec­tively sits in the ad­he­sive layer. Ex­pect to pay around £45/ m2 to £50/m2.

For fast in­stal­la­tion (and cost­ing around £55/m2 to £60/m2), a sys­tem with a mat­ting can be used that

de­cou­ples the tiles from the sub­floor. The mat­ting is laid on the floor and the wires are pushed into pre­formed cut-outs. The ad­he­sive is ap­plied to the mat­ting and, as it is not ap­plied di­rect to the sub­floor, po­ten­tial fu­ture sea­sonal crack­ing risk is mit­i­gated.

Soft fin­ishes such as car­pet, vinyl and lam­i­nate can be a chal­lenge and foiltype sys­tems are de­signed for this sce­nario. There’s no re­quire­ment for a screed with this type of so­lu­tion and you can ex­pect to pay around £40/m2 to £50/m2.

If the room is of an ir­reg­u­lar shape or there are per­ma­nent fix­tures, then a loose wire sys­tem is best-suited. The heater is a durable but flex­i­ble ca­ble that is stuck to the back­ing boards and is em­bed­ded in the lev­el­ling com­pound or ad­he­sive. In­stal­la­tion is a bit more de­tailed but the prod­uct al­lows for a lot more de­sign lay­out vari­a­tion. Ex­pect to pay around £50/ m2 to £55/m2.

The cheap­est sys­tem at around £15/m2 fea­tures a ca­ble that is bed­ded in a screed. This sys­tem has thicker wires and al­lows for floor fin­ish changes with­out dam­ag­ing the wires. The sys­tem is slow to re­act and should be de­signed for longterm space heat­ing and not for quick task heat­ing for short pe­ri­ods of time.

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