Ventilation strategies

As for living comfort at the levels of airtightness we are building to, it becomes necessary to use a whole house ventilation system. For this there are two main options; Mechanical Extract Ventilation (MEV) and Mechanical Ventilation with Heat Recovery (MVHR).

MEV uses a constantly operating fan which extracts warm moist air from the warm moist rooms (ie. bathrooms, kitchen etc) via ductwork, with fresh air effectively being sucked in via trickle vents and gaps in the structure. MEV is fairly economic to install, especially as it eliminates the need for dedicated extractors in the bathrooms. However, for very airtight buildings additional openings in the structure need to be introduced and warm stale air is replaced with fresh but cold air, thus driving heat out of the building and reducing its efficiency. As an aside to this, an MEV option is available for our heat pump which actually uses the heat from the outgoing stale warm air to pre-heat the ‘brine’ before it goes into the heat pump, thus recovering some of that energy. This is a great idea and an option well worth considering for self builders opting for a heat pump, but we eliminated it on the basis that that our first floor is largely unheated and such a system might lead to the cooling of that area via the trickle vents in the Velux windows which would need to be open for this system to work properly.

MVHR combines MEV with an intake system which supplies the ‘dry’ rooms with fresh air, preheated via a heat exchanger which takes heat from the extracted air. This is the system we have chosen, a (claimed) 95% efficient unit made by Dutch company Renovent and supplied by Ubbink in the UK. The unit has three settings and is virtually silent in operation. At the lowest setting (normal operation) it uses just half the power of a 60W light bulb and should be adequate to ‘heat’ the three first floor bedrooms alongside the heat convected from the ground floor. Other advantages are good air quality by using fresh, filtered air from outside, and the ability to use the unit to provide cooling in summer by bringing in cool air at night into a solar heated building.

Airtightness details

Having specified and designed a house to meet the AECB’s Silver Standard, airtightness plays a key role alongside high levels of insulation to achieve a low energy house. In our case we have followed the AECB’s Silver Standard construction details for timber frame buildings which advises the use of a continuous air/vapour control layer inside the building with all joints lapped, sealed and mechanically trapped.

This has probably been one of the most difficult aspects to achieve on site for our construction team which, in common with most UK builders, is simply not used to working to such a tight specification. With this in mind we opted for a solution which has largely avoided the need for specialist tapes and sealants, and in the main relies on the mechanical trapping of taped and lapped joints to provide a positive seal along with silicone sealant. We won’t really know how well this has worked until we do an airtightness test on the building, but on the basis that opening the front door feels somewhat akin to opening the door of a luxury car (ie. that air suction noise!) gives me some confidence. Also when it’s blowing a gale outside, there are no obvious draughts entering the building apart from the open trickle vents (shutters not yet fitted) and the yet to be connected stove flue.

Brickbats and Bouquets

Life is immensely busy so when we get great service from someone it is terrific and of course when we have to spend lots of time chasing people or doing someone else's job its a real pain. One of our future projects is the development of two holiday lets (more another time on those) so we're building up bank of people and places we'd like to use again. This list isn't exclusive, maybe at the end of the project we'll compose a list of the best products, people and places.

On my list for bouquets are the builder and every tradesman who has worked on our site (no kidding, I know its unusual); Sainsbury's online for kitchen appliances (subject to delivery of course); Ecoliving for the ground source heat pump which is working tremendously well.

Currently on the blacklist are B&Q's delivery service; the products are good and well priced they just don't do delivery within or close to their estimates and are a nightmare to chase.

Not for blacklisting but 'could do better' - the timber frame manufacturer is not high on the favourites list but the builder has had the burden of chasing them and the joiners have had the problem of insufficient supplies. The Architect has been on site only three times since Christmas so there's a bit of a gap on the project management which we and the builder have filled. That's fine 'cos we have filled the gap but isn't the service signed up for.

And the weather has been pants since Christmas too!

Internal and External Finishes

We have had snow in the early part of this week but this isn't it! Here we're got the roughcasters flinging the wet dash render onto the east elevation. You can see where they completed one area at the end of last week as the mix dries whiter than when it is applied (thankfully otherwise we'd have a magnolia house!). Its a very messy task.

The larch cladding on the SW corner - this is really looking fabulous and we're very pleased with the choice of timber, its profile and the joiner's work. The timber frame company haven't been doing such a good job on the timely supply of the correct quantities of materials but this appears to being resolved after many calls from our builder. The timber itself has come from Russwood who are based in North Perthshire.

Not a great photo because of the light bounce but this is the toile negro tile which we choose for the ground floor bathroom. It looks terrific in place, especially in the shower with a single spot shining down.

one ensuite shower area

paint colour Winter Teal 5 for Finlay's room.......Dulux have done a fine job with that colour matching and shading/colour depth system as its a terrific marketing tool in providing the customer with thousands of options....so all our paint colours are coming from them and the marketing tool has worked!