Green build­ing ma­te­ri­als

Look­ing to make your self-build or ren­o­va­tion as sus­tain­able as pos­si­ble? Nigel Grif­fiths re­veals the es­sen­tials you need to know when spec­i­fy­ing what goes into your new home

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Spec­i­fy­ing sus­tain­able con­struc­tion op­tions for your home’s ex­te­rior and in­te­rior could en­hance your fam­ily’s well­be­ing

If you want a truly sus­tain­able, healthy home, then ev­ery as­pect of your project needs to be con­sid­ered in de­tail – from low-en­ergy de­sign strate­gies through to the prod­ucts and fin­ishes that go into both the struc­tural fab­ric and the in­ter­nal fit-out.

When it comes to spec­i­fy­ing prod­ucts, there are a num­ber of core fac­tors to keep at the front of your mind. How much car­bon is con­sumed in their fab­ri­ca­tion?

Are they made from re­new­able re­sources? And how re­cy­clable are they at the end of their use­ful life?

Health is an­other vi­tal area that should be top of ev­ery­one’s list when it comes to green con­struc­tion. What­ever we build, and what­ever we use to con­struct it, a home should en­hance the oc­cu­pants’ well­be­ing. Avoid­ing toxic ma­te­ri­als, pro­vid­ing ther­mal com­fort, en­sur­ing a good sup­ply of fresh air and de­sign­ing in plenty of day­light will all help to de­liver a home that’s sus­tain­able and makes a pos­i­tive con­tri­bu­tion to phys­i­cal and men­tal health.

Struc­tural op­tions

In terms of the main shell of your home, the rather vague phrase ‘green build­ing ma­te­ri­als’ could cover any­thing from straw bale con­struc­tion through to brick and block sys­tems. At a re­cent Build It Live show, I met a cou­ple who were plan­ning to con­struct their home us­ing hempcrete; and an­other who were go­ing to have a crack at straw bale – both ex­cit­ing but chal­leng­ing routes to build­ing a new house (best of luck to you if you’re read­ing this!).

Most peo­ple, how­ever, will be think­ing in terms of more con­ven­tional tech­niques, such as ma­sonry or tim­ber frame. But there’s a point to men­tion­ing those cou­ples: they’re us­ing waste prod­ucts as their pri­mary build­ing ma­te­ri­als, which will hugely re­duce the en­vi­ron­men­tal im­pact of their projects.

In terms of the cir­cu­lar econ­omy, it also en­cour­ages re­cy­cling by pro­vid­ing a valu­able mar­ket for waste prod­ucts.

We can use this kind of ap­proach when de­cid­ing on all as­pects of the con­struc­tion process, from foun­da­tions to fur­nish­ings. Start by reusing what you’ve got, then stick to re­new­able re­sources with min­i­mal en­vi­ron­men­tal im­pact for the rest. For in­stance, tim­ber (and tim­ber waste prod­ucts, such as wood-fi­bre in­su­la­tion) is highly sus­tain­able, pro­vided there’s ad­e­quate re­plant­ing. The

FSC mark is a re­li­able guide; although there are some other cer­ti­fi­ca­tions that are equally strong, such as PEFC.

En­gi­neered tim­ber prod­ucts, such as glu­lam beams, are also able to do the job of steel in many de­signs – thus elim­i­nat­ing the need for a non-re­new­able re­source. And if you opt for a light­weight fram­ing sys­tem, this should re­duce the amount of con­crete re­quired for foun­da­tions (some sys­tems dis­pense with the con­crete al­to­gether).

If you are com­mit­ted to build­ing your project in ma­sonry, there are op­tions to re­duce en­vi­ron­men­tal im­pact. You could opt for re­claimed bricks, for in­stance, or se­lect blocks with high re­cy­cled con­tent. And when it comes to foun­da­tions, there’s even a damp-proof mem­brane avail­able made from 100% re­cy­cled plas­tic.

In­su­la­tion

Rigid in­su­la­tion is of­ten used in new con­struc­tion in the UK. It’s ex­cel­lent at its job of re­tain­ing heat, but if sus­tain­abil­ity of ma­te­ri­als is a key con­sid­er­a­tion for your project, then it’s worth not­ing that these prod­ucts are de­rived from oil – a non-re­new­able re­source. A rel­a­tively high amount of en­ergy is needed to pro­duce it com­pared to many other op­tions. In ad­di­tion, rigid in­su­la­tion is usu­ally made with plas­tics that are dif­fi­cult – and some­times im­pos­si­ble – to re­cy­cle ef­fec­tively.

There are plenty of al­ter­na­tives, many of which are par­tic­u­larly suited to tim­ber fram­ing. Houses, schools and com­mu­nity cen­tres have all been con­structed with re­cy­cled news­pa­per in­su­la­tion, for ex­am­ple, which is a great use of a waste prod­uct. One de­vel­op­ment I did with this ma­te­rial was judged at the time to be the most en­ergy-ef­fi­cient street in the coun­try.

Ver­sions made of wood wool and hemp wool are all use­ful al­ter­na­tives, and some come in rigid board for­mats. De­pend­ing on the over­all con­struc­tion, some of these prod­ucts have the abil­ity to ad­sorb mois­ture or pol­lu­tants, which can help to min­imise con­den­sa­tion and cre­ate a cleaner, more bal­anced in­ter­nal environment.

That’s not to say there’s any­thing wrong with good old min­eral wool. It’s vapour open, comes from a plen­ti­ful source and in many sit­u­a­tions will be the best choice – espe­cially where fire rat­ings are im­por­tant.

Roof­ing ma­te­ri­als

Clay tiles and nat­u­ral slates tend to have the low­est em­bod­ied en­ergy when it comes to roof cov­er­ings, though most of the slate used in UK con­struc­tion is now im­ported from cheaper sources (adding to the car­bon costs).

Con­crete tiles are more en­ergy-in­ten­sive to pro­duce, but in any case are fall­ing out of fash­ion, as they aren’t the most durable op­tion for be­spoke homes (the colour will fade, for in­stance). Metal roof­ing is very pop­u­lar at present, but bear in mind that the likes of zinc and cop­per are high­en­ergy prod­ucts and non-re­new­able re­sources.

For flat roofs, EPDM (a syn­thetic rub­ber) is so much longer last­ing than tra­di­tional felt that its over­all im­pact is likely to be lower over the life­span of a build­ing. These qual­i­ties more than jus­tify the ad­di­tional cost.

Win­dows & doors

The same ad­vice ap­plies to win­dows and doors as to the other parts of your home’s struc­tural shell. Tim­ber is a

plen­ti­ful and re­new­able re­source, and can be used to pro­duce long-last­ing fen­es­tra­tion. Con­versely, plas­tic ver­sions re­quire a lot of en­ergy to fabri­cate. What’s more, they are dif­fi­cult to re­cy­cle and the ma­te­rial gives off toxic fumes when burned.

If you own a Vic­to­rian or Ed­war­dian home, it’s easy to think that dam­aged orig­i­nal win­dow frames have rot­ted. In fact, when prop­erly main­tained, these units can last in­def­i­nitely. Even if they’ve not been kept in good or­der, any rot is nor­mally con­fined to the sill and lower sec­tions of the sashes; and can be eas­ily re­paired by an ex­pe­ri­enced car­pen­ter.

Our fore­bears used good qual­ity slow-grown tim­ber, but this wasn’t the case in the 1960s and 70s. Win­dows from that era tend to rot quicker once the paint skin is com­pro­mised; but this isn’t a fair re­flec­tion of the per­for­mance mod­ern tim­ber op­tions can of­fer. Ex­te­rior paint tech­nol­ogy has im­proved markedly in the last 20 years, so new frames re­quire much less fre­quent main­te­nance.

Plas­tic win­dows and doors, on the other hand, are much more dif­fi­cult to suc­cess­fully re­pair or re­fresh. Metal ver­sions do not suf­fer from these dis­ad­van­tages – plus their in­nate strength can open up more de­sign pos­si­bil­i­ties, and if you’re us­ing alu­minium they’ll be re­cy­clable. How­ever, they do have a high em­bod­ied en­ergy.

Glaz­ing, of course, has an im­por­tant role to play in terms of con­tribut­ing to your home’s com­fort and day­light­ing lev­els – which are vi­tal to health and well­be­ing. Spec­i­fy­ing en­ergy ef­fi­cient units is a must for most projects; but

re­mem­ber your win­dows and glazed doors will only per­form up to the ex­pected stan­dard if they’re prop­erly in­stalled. Their po­si­tion and ori­en­ta­tion will also de­ter­mine how much nat­u­ral light en­ters and flows through your home, along with the po­ten­tial for free boost of heat via so­lar gain. These con­sid­er­a­tions need to be bal­anced against pos­si­ble over­heat­ing, so it’s im­por­tant to work with spe­cial­ists to get the de­sign right.

Ven­ti­la­tion & healthy fin­ishes

Chem­i­cals that evap­o­rate into the air are known as volatile or­ganic com­pounds (VOCS). They oc­cur nat­u­rally, so they are not all harm­ful – but new build­ings can con­tain high lev­els of VOCS that are detri­men­tal to health (espe­cially formalde­hyde, which is a recog­nised car­cino­gen).

The bad VOCS can cause asthma and other dis­eases, but their level in­doors is de­pen­dent on the qual­ity of ven­ti­la­tion, as much as on the sources of the com­pounds them­selves. A re­port from the Royal Col­lege of Physi­cians, ti­tled Ev­ery Breath We Take, flags up in­door air qual­ity as po­ten­tially a much greater threat to health than out­door air.

Me­chan­i­cal ven­ti­la­tion sys­tems are avail­able that can main­tain a fresh sup­ply in air­tight homes (even fil­ter­ing out pollen, for in­stance); and you can opt for heat re­cov­ery ver­sions to fur­ther boost com­fort lev­els. This is a com­mon and ef­fec­tive choice for self-builders. Al­ter­na­tively, the likes of Stom­mel Haus use highly in­su­lated, air­tight yet breath­able struc­tural fab­rics for their homes, whilst avoid­ing toxic prod­ucts. This cre­ates a healthy in­door cli­mate with­out the need to rely on me­chan­i­cal ven­ti­la­tion.

In terms of fin­ishes, it’s now com­monly un­der­stood that con­ven­tional paints and other coat­ings of­ten con­tain high lev­els of VOCS. There are plenty of good-qual­ity re­place­ments, how­ever: gen­er­ally, plant-based, wa­ter­borne op­tions are the most eco-friendly choices.

Some en­gi­neered wood prod­ucts, such as chip­board, also con­tain high lev­els of VOCS. This means cer­tain parts of the home, such as kitchens, are more likely to be af­fected. To min­imise their pres­ence, con­sider switch­ing to ply­wood or low-voc MDF for the car­cass­ing, and prod­ucts such as solid wood or stone for work­tops.

Con­ven­tional car­pets of­ten con­tain fire re­tar­dants, fungi­cides and pes­ti­cides, so look at us­ing eco-friendly al­ter­na­tives such as jute or sisal. Wool rugs are also avail­able with­out cock­tails of toxic chem­i­cals.

Fur­ni­ture, ad­he­sives, clean­ing prod­ucts and air fresh­en­ers can all con­tain harm­ful VOCS, too, so it’s im­por­tant to bear this in mind once you’ve moved in. Hav­ing cre­ated a sus­tain­able, healthy home, it would be a shame to in­tro­duce tox­ins af­ter­wards.

Con­clu­sion

When you look at a wall, you can’t tell whether the blocks that went into it have a high re­cy­cled con­tent or whether the paint was low in VOCS. Nei­ther can you tell if wood prod­ucts have been re­spon­si­bly sourced at first glance; and struc­tural tim­ber can’t even be seen.

In other words, true sus­tain­abil­ity is hid­den. It’s all about de­sign and the choices you make in the pro­cure­ment process – and there’s lit­tle point pay­ing it lip ser­vice. I re­cently heard of a cou­ple who had in­stalled so­lar elec­tric pan­els on the north­ern el­e­va­tion of their roof, where they’d get barely any sun and pro­vide piti­ful pay­back on the en­ergy that went into man­u­fac­tur­ing the ar­ray. When this was pointed out to them they agreed, but said their friends wouldn’t be able to see it if it was in­stalled else­where. Now that’s top qual­ity eco-bling for you!

Above: Win­ner of the 2017 Build It Award for Best Eco Home, this project by Beattie Pas­sive fea­tures a fac­to­rypro­duced tim­ber frame. The fin­ished house ex­ceeds Pas­sivhaus re­quire­ments for air­tight­ness and is so well-in­su­lated it doesn’t re­quire con­ven­tional heat­ing to pro­vide year-round com­fort. Right: Ger­man home sup­plier Baufritz uses breath­able, vapour-open yet air­tight tim­ber pan­els – com­plete with com­pressed wood shav­ing in­su­la­tion – for its sus­tain­able homes

Be­low: Chalk Paint by An­nie Sloan has a min­i­mal VOC con­tent at just 0.02g/l; as op­posed to the 30g/l al­lowed un­der UK reg­u­la­tions

Above: Welsh Slate’s strik­ing Pen­rhyn Heather Blue tiles add plenty of kerb appeal to this new home – and they’re a nat­u­ral, Bri­tish­made prod­uct

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