cre­aT­ing a warmer home

Work be­gins on in­su­lat­ing and drylin­ing Ian Rock’s large new ex­ten­sion, while he turns his at­ten­tion to spec­i­fy­ing a wood stove

Homebuilding & Renovating - - ON SITE -

The last few weeks have wit­nessed a flurry of syn­chro­nised ac­tiv­ity as work on the in­te­rior of our ex­ten­sion shifted up a gear.

This fol­lows a fairly lengthy spell largely de­voted to find­ing trades and ob­tain­ing quotes.

De­ploy­ing in­di­vid­ual trades­peo­ple is a bit like con­duct­ing an or­ches­tra, al­beit one res­onat­ing to the sound of power tools. Lots of in­di­vid­ual con­tri­bu­tions need to be co­or­di­nated in tune with the de­signer’s mas­ter­plan to ul­ti­mately cre­ate a har­mo­nious three di­men­sional build­ing, hope­fully with­out too many bum notes.

in­su­laT­ing: a mam­moTh Task

By far the big­gest un­der­tak­ing on the in­te­rior of our ex­ten­sion is the com­bined job of in­su­lat­ing, board­ing, drylin­ing and plas­ter­ing — a mam­moth task for which we ap­pointed lo­cal plasterer Jamie Bo­som­worth. The first leg of this marathon re­quires ac­cu­rate cut­ting and plac­ing of 120mm-thick

Kingspan phe­no­lic foam in­su­la­tion boards be­tween the rafters of all three main roof struc­tures, tak­ing care to first leave 20mm ven­ti­la­tion paths un­der the breather mem­brane. This is not an easy job at the best of times, par­tic­u­larly when it comes to in­su­lat­ing slop­ing ceil­ings at high level.

Prior to this, elec­tri­cians Alex and Sam com­pleted the first fix ca­bling within the sched­uled three and a half day time­frame and were duly re­warded for their ef­forts by Mrs Rock bear­ing a steam­ing plate of hot sausage rolls (in ad­di­tion, of course, to their agreed pay­ment!). Elec­tri­cians need to work closely with plas­ter­ers to co­or­di­nate all the var­i­ous light­ing points and switches, and I no­ticed that each elec­tric cable had a ref­er­ence marked on it in black felt pen to aid iden­ti­fi­ca­tion at se­cond fix once en­gulfed be­hind acres of plas­ter­board.

Af­ter a week and a half work­ing flat out, Jamie fin­ished the first phase of in­su­lat­ing all the slop­ing ceil­ings. The key thing with in­su­la­tion is not to leave gaps that moist air from the rooms can seep through and then con­dense in the cold spa­ces be­hind, so we made sure that any un­even edges were sealed with ex­pand­ing foam.

The next job was to line the un­der­side of the part-in­su­lated ceil­ings with a vapour bar­rier sheet. Although the ven­ti­la­tion space re­tained above the in­su­la­tion should, in the­ory, waft any hu­mid air away, fit­ting a vapour con­trol sheet is ad­vis­able as a ‘belt and braces’ pre­cau­tion. To un­der­line the im­por­tance of this, Jamie re­counted a story about a damp prob­lem he’d come across in a re­cently in­su­lated roof. Ap­par­ently when he started hacking off the damp ceil­ing plas­ter a del­uge of trapped wa­ter came drip­ping down — the re­sult of ‘in­ter­sti­tial con­den­sa­tion’ caused by a lack of any vapour con­trol layer to pre­vent hu­mid air get­ting through.

We knew Jamie had other jobs rapidly pil­ing up so it was agreed that he would re­turn in two weeks’ time to com­mence the next phase.

choos­ing a wood­burner

As with most big-ticket pur­chase de­ci­sions, choos­ing a wood­burn­ing stove in­volves a great deal of huff­ing and puff­ing, re­search­ing what seems to be an in­fi­nite va­ri­ety of com­pet­ing prod­ucts. Splash­ing cash on de­sir­able fit­tings for your new home ex­ten­sion should be a plea­sur­able pas­time, yet mak­ing the right choice isn’t al­ways straight­for­ward.

What helped dur­ing our search for a wood­burner was that we pretty much knew what we wanted — a sleek modern curved de­sign in tra­di­tional black, with a de­cent-sized glass door to view the flames, an in­te­gral log store, plus the op­tion of an ex­ter­nal air sup­ply, all within a price range of £600 to £900 (prefer­ably Bri­tish made). Af­ter what seemed like a life­time scru­ti­n­is­ing end­less ad­verts and web­sites, and ag­o­nis­ing over tech­ni­cal spec­i­fi­ca­tions we nar­rowed it down to one clear con­tender: the con­tem­po­rary ‘Arc­tic’ stove range dis­trib­uted by Greymetal. The only com­pro­mise was with my pa­tri­otic sen­si­bil­i­ties as the stoves are im­ported from ABX in the Czech Repub­lic.

Although the open plan ground floor space is pretty large, the stove shouldn’t have to work too hard be­cause the pri­mary warmth will be pro­vided by un­der­floor heat­ing. Also, the ex­ten­sion de­sign ex­ceeds ther­mal ef­fi­ciency tar­gets so heat re­ten­tion should be very good. Wood­burn­ing stoves are renowned for belt­ing out in­cred­i­ble amounts of heat and are ac­tu­ally most ef­fi­cient when run­ning close to peak ca­pac­ity, so we opted for a rel­a­tively con­strained 5kW stove. This also saves some weight at ‘only’ 110kg (com­pared to a back­break­ing 170kg for the 8kW ver­sion).

Be­com­ing so en­grossed in choos­ing your stove means there’s a risk you can take your eye off the ball when it comes to the de­cid­edly less sexy sub­ject of spec­i­fy­ing the cor­rect type of flue that it con­nects to. De­sign­ing the flue route and cal­cu­lat­ing the var­i­ous dif­fer­ent com­po­nent lengths, brack­ets and fix­ings takes a great deal of thought (and usu­ally best left to your HETAS in­staller). It’s not al­ways ap­pre­ci­ated that the cost of buy­ing all the flue ma­te­ri­als can eas­ily ex­ceed the price of the stove, and the best prices I could find for these were from a com­pany called Fire­box. Be­cause we’d used the Selkirk brand of 150mm twin wall flues for the ini­tial lengths in­stalled at roof level, we had to stick with the same man­u­fac­turer be­cause dif­fer­ent brands of nom­i­nally iden­ti­cal twin wall flues don’t in­ter-con­nect.

geT­Ting ready for The in­sTal­la­Tion Be­fore book­ing a firm date for a HETAS-reg­is­tered heat­ing en­gi­neer to in­stall the flue and stove there were one or two out­stand­ing jobs on my DIY list, such as trim­ming a cou­ple of bed­room floor joists in the path of the flue to pro­vide the nec­es­sary 50mm safety buf­fer (since our orig­i­nal de­sign hadn’t al­lowed for a wood­burn­ing stove). Most stoves take their air for com­bus­tion from the room, so air vents need to be in­serted in the main walls. This strikes me as slightly bonkers given all the trou­ble de­sign­ers go to, to meet U value heat loss tar­gets. Modern sus­pended ground floors with a ven­ti­lated void un­der­neath can pro­vide a use­ful source of air and it was an easy job to in­stall the nec­es­sary duct­ing. This just left one small dilemma. The flue and stove need to be in­stalled be­fore the ceil­ings are plas­ter­boarded but the ground floor is still a cou­ple of months away from be­ing in­su­lated, screeded and tiled.

So to give the stove some­thing to stand on, the sec­tion of floor di­rectly un­der­neath needed to be built up to the fin­ished floor level and a suit­able hearth con­structed. It’s not un­known for pro­mo­tional shots of stylish stoves in ad­ver­tis­ing ma­te­rial to in­ad­ver­tently omit the non-com­bustible hearths re­quired by Build­ing Reg­u­la­tions, which ob­vi­ously isn’t an op­tion in the real world.

Af­ter briefly flirting with glass hearths we plumped for tra­di­tional creamy traver­tine stone, how­ever it soon be­came ap­par­ent that if you don’t want to buy a room­ful of the stuff, sup­pli­ers sim­ply aren’t in­ter­ested. On the off-chance I popped into the lo­cal show­rooms of Stoneworld of Ox­ford­shire but it tran­spired that they didn’t have the prod­uct I wanted. Then, as I headed for the door, Rob, the af­fa­ble pro­pri­etor to whom I’d been chat­ting, sud­denly re­called that they had some small ready­made-up dis­play sam­ples go­ing beg­ging. “These should do the trick,” he beamed benev­o­lently.

nexT monTh: firsT fix plumb­ing

“spend­ing cash on de­sir­able fit­tings should be a plea­sur­able pas­time, yet mak­ing the right choice isn’t al­ways straight­for­ward”

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