The Green Room – why is it warm and toasty?


The Green Room has been built with a strong focus on very high levels of insulation and air-tightness in an attempt to reduce the running cost and our reliance on fossil fuels to an absolute minimum

The building utilises Structural Insulated Panels (SIPS) as the main structural elements for walls and roof.


A SIP panel comprises Polyurethane Foam Insulation sandwiched between two layers of Orientated Strand Board (OSB). The resultant material is both very rigid and highly insulating. It is a development of an idea originally proposed by the famous American architect Frank Lloyd Wright. To supplement the already high insulation values of this material we have added a further 50mm of urethane foam insulation inside the building to make it really cosy.

Set up

The floor is also highly insulated with urethane materials and is finished with a self-levelling screed that contains hot-water pipes forming a large heat-store and radiator combined. Heat energy is supplied by storing water heated overnight by off-peak electricity, in a 300 litre insulated tank with an ordinary programmer that calls for heat and a thermostat that regulates the room temperature. The windows are low u value and the best we could afford.


Because we have made the structure air-tight to a very high level we have fitted a ventilation system that introduces fresh air from outside to make the room comfortable. This system captures heat energy from the outgoing stale air to pre-heat the incoming fresh air at an efficiency of over 90% and in summer it allows cool air to enter without any pre-heating to maintain maximum comfort levels and avoid over-heating.


There is a 4.0 kW Solar Photovoltaic system on the south facing roof that we hope will generate enough electricity to make the building self-sufficient in energy for both heating and lighting over the yearly cycle. Electricity from our panels is sold to the grid, but only after we have satisfied our needs in running the building. We will measure this energy use and report on the balance achieved between use and production at the end of the first year.


The outside of the building is clad in natural Larch planks that have been purposely left “as-sawn” so that they hold a very high coat weight of paint for maximum long-term durability. The roof is made of stainless-steel that is “roll-bonded” with a zinc surface that prevents it from being too shiny on a sunny day and allows the material to be solder-joined when necessary.

Throughout the design of this building we have attempted to use sustainable methods of construction that minimise the embodied energy in the materials and, at the same time, deliver a building with low maintenance costs and a minimal carbon footprint..

We have tried to incorporate as many good ideas as we could, but there is always room for improvement. Please feel free to let us have you suggestions and ideas for the next one as well as improvements we may incorporate to refine this one.

Stewart McKenna Jan 2014

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s