Building for a zero carbon future

Would you like to live or work in a warm, draft free, healthy space that is easy and cost effective to heat?

Transforming our leaky buildings to make them clean, green, healthy and affordable to heat is a big project, but we have all the knowledge and tools we need to do it – and it offers us many additional benefits. Here is a selection of good ideas on how we can transform our existing buildings and build new ones in much more energy efficient ways, so we have better places to live and work, and support the shift to a zero carbon future. Continue reading “Building for a zero carbon future”

Celebrate with CAT’s architects of the future

CAT’s Architecture Professional Diploma students celebrate the end of their studies with a private view of their work and a party at CAT on 20th January.

This unique event invites industry VIPs, students, local people and friends of CAT to view the final projects of these up-and-coming architects after 18 months of intensive study. Transforming study rooms into exhibition spaces their inspirational designs and models will be available to view with the students themselves on-hand to talk guests through their visions. This will be a unique insight into the ideas of the architects of our future. Continue reading “Celebrate with CAT’s architects of the future”

Ask an expert: eco refurbishments

Want to refurbish your home in a sustainable way? With over 25 years’ experience, including as tutor on CAT’s Eco Refurbishment course, Nick Parsons has some great advice – here are his top tips.

1. Make it air-tight.

Stop unintentional ventilation (this involves designating an air-tightness layer – and sticking to it!) and design in sufficient intentional ventilation. For a whole-house retrofit this will almost certainly be whole-house mechanical ventilation with heat recovery (MVHR), but for incremental retrofits, or those with less stringent air-tightness targets, passive ventilation may suffice.

2. Insulate, insulate, insulate!

Don’t automatically believe that Building Regulations standards of insulation are enough. They aren’t bad, but in many cases we should be aiming for far better. If you have the space – and the money – Passive House levels of insulation (U values of 0.15W/m2K or less) and air-tightness (less than one air change per hour for the refurbishment EnerPHit standard) can dramatically reduce your heating requirements and massively improve comfort.

External insulation of solid walls will make your house look a bit different. Ducks are optional.
External insulation of solid walls will make your house look a bit different. Ducks are optional.

3. Insulate externally! (Unless you can’t…)

External insulation of solid walls, if detailed properly, puts the entire building fabric inside a warm ‘tea-cosy’. But it does make your house look different.

4. Risk-manage your insulation

If you have to insulate your solid walls – or sometimes even add insulation to your cavity walls – internally, excellent detailing is critical. Insulating walls internally makes the room warmer but makes the walls themselves colder and more at risk of interstitial condensation – condensation within the new thickness of the wall, behind the insulation. This can rot joist ends and other embedded timbers, and maybe grow mould. Cold walls may also suffer from deterioration of the masonry due to frost damage.

If you insulate internally, make the whole process a documented risk management exercise – identify the risks, identify control measures and document how you will implement them. In certain circumstances, consider embedding sensors and monitoring equipment in hidden timbers so that you can know if moisture levels become critical. The expense may be off-putting, but it will be a great deal less than the remedial works if you have inadvertently shortened the life of your house by doing what you thought was the ‘right thing’.

In general the use of ‘breathable’ (water-vapour-permeable) insulants such as wood-fibre or cork may reduce risks, but very careful detailing is still required.

Greater risks exist with non-breathable insulants, but if they are installed with extreme care, the risks may be capable of being ‘managed’ and minimised. If you are installing them yourself, take advice from someone with a lot of experience. If someone else is installing them for you, are they experienced with such boards? Do they fully understand interstitial condensation and vapour control layers (VCLs)? Have they read the manufacturer’s installation instructions?

5. …and consider its environmental impact

Materials such as plastic insulation – made from crude oil – are high in embodied energy (the energy, including transport, used to get the product from raw material to the merchant’s shelf), but look at the units used. If the measure is weight, a heavy bit of ‘green’ insulation may be higher in embodied energy than a much lighter piece of ‘non-green’ insulation.

You may in any case wish to avoid wherever possible materials made from petrochemicals.

But ‘environment’ may mean more than ‘the world in general’. What about your immediate living environment? You may feel better in a room lined with vapour-permeable, moisture-buffering wood-fibre than in a room lined with petrochemical-based insulation.

6. Minimise thermal bridging

dscf3495You may believe – perhaps because your builder or consultant told you – that having low (good) U values guarantees good performance but thermal performance may be let down by weak-points in the insulation layer. Typically this would be where partition or party walls interrupt the insulation layer, where walls turn into windows or doors, or where internal insulation has to be thinner to accommodate fixtures or fittings. In practice, your U value may not be as low as you believed it to be.

The picture on the left shows: on the left, a wall prepared for insulation to ‘return’ on to internal wall to cloak the thermal bridge; in the middle, Pavadentro wood-fibre board prior to plastering; and on the right an existing brick wall with a lime ‘parge coat’ (air-tightness layer) to reduce air-leakage through voids in the brick wall.

 

7. Minimise thermal by-pass

Thermal by-pass, or ‘wind-wash’, occurs when cold air is allowed to get to the ‘warm side’ of the insulation. This can best be explained in two scenarios:

The first is a loft-conversion. The eaves areas are cold voids. The stud walls to the room (which are built off the floorboards) have been insulated to a good standard but there is only 100mm of insulation between the 150mm floor joists.

The ventilation air which enters at the eaves vents (a good ‘howling gale’ to keep all the timbers healthy) can blow directly under the floor of the heated bedroom, providing instant cooling!
Small pieces of plywood or similar board, sealed at all perimeters, placed between the joists at the edge of the floor on both sides of the bedroom will cure the problem. ‘Plugs’ of quilt insulation placed in the gaps will not do such a good job (as quilt insulation is generally air-permeable), but will be better than nothing. Once these gaps have been sealed, the insulation should in any case be increased to approximately 300mm.

The second scenario involves insulation to the sloping ceilings above an attic bedroom, carried out, as the law requires, by roofing contractors when re-roofing the house.

The house was sold and the new owner decided to remove all the attic ceilings. All but about six of the sheets of insulation fell out from between the rafters. What this tells us is that, while the insulation was in place, the cold air in the ventilation gap between the insulation and the slates was able to migrate to the warm side of the insulation, rendering the insulation almost useless.

8. Plan to do it all!

Many insulation plans are carried out incrementally, perhaps as other work is required, or when a room needs comprehensive re-decoration or (externally) when the cost of re-pointing an elevation can be avoided and put towards the cost of externally insulating that elevation.

When planning your works, ideally plan to do the whole house, even if you know it is going to take you 10 years to achieve it. I’m 29 years in and starting to re-do the internal insulation using better materials and methods than were available in 1987! Plan how your individual works are going to ‘knit together’ so as to limit thermal bridges, where condensation and mould may otherwise occur.

Above all, you don’t want your works – undertaken with the best of intentions – ultimately to shorten the life of your house.

image1About the author
Nick Parsons has worked in energy-efficient and sustainable building and renewable energy for over 25 years. He provides consultancy and project management services to individuals, small businesses and community organisations and is a regular tutor at CAT and elsewhere. See www.sustainablebuilding.org.uk for details.

CAT courses
The next eco-refurbishment course with Nick takes place from 4th to 7th November. For more information and to book, please visit http://courses.cat.org.uk/ or call us on 01654 704966.

Roundwood timber frame – new course

We’re really looking forward to the crew from Ty Pren Workers’ Co-op joining us in a couple of weeks to teach our new Roundwood Timber Frame course.

This really is do-it-yourself building – we’ll start off in the woods learning how to choose the right trees for construction and by the end of the week we’ll have completed the frame for a small building.

If you’re visiting CAT on the week of 22nd to 26th August, you might just get a glimpse of the build taking place, and if you’d like to join the course there are still a couple of spaces left.

Here are a few pics from recent Ty Pren projects to get us all in the mood…

TyPrenBuild   Roundwood-Sheppards-HutTyPrenBuild2   Joints1

TyPren-Roundwood Ty-Pren-Roundwood1