AW Laing wins Construction Contract for new Eco-Croft House in Boat of Garten

AW Laings have secured the Contract to build a new 4 bedroom Croft House on a bare-lands croft site in the heart of the Cairngorms National Park. The contract is due to start January 2010, weather and snow permitting. 

The design of the new dwelling is intended to recreate the traditional building form and materials associated with rural Steadings throughout Strathspey. However the construction of the new dwelling is contemporary in its use of materials and their associated energy efficiency and environmental performance.

It is hoped that this project will help the CNPA set new sustainable design standards: at the core of these the minimisation of CO2 emissions will be achieved by adopting a 3-layer strategy:

• Build Tight & Insulate Right – reduce demand for energy input
• Use of Renewable Energy – and plan for future energy supplies
• Use Local Skills, Materials & Suppliers – minimise carbon miles

1 - Dwelling Construction - Build Tight & Insulate Right 

The timber frame construction is insulated to current building regulations mineral wool products with formaldehyde-free binders and made from bio-based materials (instead of petroleum-based chemicals) which is up to 70% less energy intensive. These insulation products contain no dye or artificial colour, are free from CFC’s, HCFC’s and any other material with ozone depletion potential in its manufacture and content: classified as Zero ODP and Zero GWP.

In addition to this basic level of insulation a second internal wrapping layer of insulation has been applied. This secondary insulation material eliminates all thermal bridging as it is applied to the inside face of the structural frame construction; performs as internal ‘air barrier’ ensuring airtight construction and provides for the ducting of all electrical & plumbing services ensuring detailing that prevents air leakage of the construction system. This insulation material comprising outer layers of coated metallised film with the core of the product consisting of layers of polyester fibre wadding separated by metallised film layers.

The novel combination of these insulation systems provides a cost effective super-insulated building envelope and significantly reduces the energy load required for heating purposes.  

2 - Renewable Energy – Heating & Hot Water Systems

A heating strategy that balances the type of dwelling, the site-specific location and the requirements of seasonal variation has been developed. Each of the systems has been chosen to operate with degrees of efficiency depending on the time of year, outdoor air temperature and homeowner preferences.

A high efficiency wood burning stove located in the principal warm / living space at the centre of the building is used in conjunction with a ventilation heat recovery system augmented by geothermal ground collectors heat-pump and solar panels to provide a seasonally balanced and resource efficient heating & hot water system. The ventilation heat recovery system eliminates the need for multiple envelope penetrations and electric fan motors as required by traditional room extract vents.

3 – Use Local Skills - Materials & Suppliers 

The main dwelling construction uses C16 grade structural timber frame construction. Only this grade of structural timber can be sourced from local sawmill suppliers. External building timberwork & cladding is specified as Scot-Larch sourced by Russwood Ltd in Newtonmore.  Overall a light-weight on-site construction system requiring no specialist installers, equipment or lifting equipment. 

The Main Contractor for the project is a well known family business A W Laing, based in Grantown-on-Spey. Each of the sub-contracted Trades is based within a 20mile radius of the site with the associated multiplier effect of the local supplier network, ensuring where possible that the value of this small project is retained within the Cairngorms National Park economy.

Greig Munro, for AffordableTM Ltd - Chartered Architects