About Heat Loss in Timber Garden Offices

What is meant by a ‘warm’ office?

A tin hut in the midst of a Siberian winter could be considered ‘warm’ if adequately heated but it could not be considered ‘efficient’. Once the heat source was turned off it would lose heat very rapidly.
Timber is not a very good insulator and timber log cabins can be considered ‘warm’, just so long as adequate heat is applied to balance the heat loss and this can be considerable!

WHEN Garden Offices UK  refer to a warm building we mean one that needs very little heat to balance heat loss. This is achieved by fantastic insulation in floor, walls and roof. In this type of building the heat given off by the occupants, lighting and equipment makes a significant contribution.

You will find that our smaller offices, once up to a comfortable temperature, can be heated just by lighting and computer equipment, even in the depths of winter. That is what WE call warm.

It is important to make the distinction because by putting an office in your back garden you will have six surfaces to lose heat from and it is therefore important to choose an office which will keep this heat loss to a minimum both for the sake of the environment and your pocket.

What does insulation in garden offices really do?

Thermal Insulation resists the flow of heat. It slows the passage of heat. Heat is a form of energy.  It always travels from hot to cold – flowing outward in winter and inward in summer. By reducing heat flow, a properly insulated office uses less energy than a poorly insulated one.

Why do we consider that our garden offices are better insulated than those of our competitors?

Our garden offices, summer houses, home gyms and timber rooms have a virtually continuous envelope of 100 mm insulation in floors, wall and roof.  They are constructed of SIPs.

Compare the use of SIPs with a  traditionally constructed timber framed office.  Traditional timber framed offices are constructed using timber posts at 600 mm centres with glass fibre or rock wool insulation placed between these posts.

Traditional timber framed offices are inferior for the following reasons:

1. The way the adjacent panels are fitted together can leave an air gap between them..
2. The timber studwork (posts) make up about 15% of the surface area of the wall and timber is not a good insulator, see table below.
3. Glass fibre and rock wool insulation is not nearly as an efficient insulation as the same thickness of polystyrene.
4. Glass fibre and rock wool insulation tends to sag over time leaving an uninsulated pocket at the top of the panel (just where most heat would be lost).

What is the measure of insulation?

‘R’ values and ‘U’ values are the measurement of how a material resists heat loss. The ‘R’ value is a measure of the resistance to transfer of heat from one surface of the material to the other. The higher the value the better the insulation properties the material has.

‘R’ and ‘U’ values of various materials:

Material	‘R’ value the higher this value the less heat lost.	‘U’ value the lower this value the less heat lost.
12 mm (1/2”) plasterboard	0.45	2.22
12 mm (1/2”) OSB (Oriented Strand Board)	0.63	1.58
89 mm (3.1/2”) softwood	4.50	0.22
100 mm (4”) softwood	5.00	0.20
100 mm (4”) traditional timber frame panel with glass fiber batts/15% timber and 12 mm ply wind bracing	Assumes no air leakage 8.33	0.12
100 mm (4”) fibreglass/rockwool batt	9.42	0.106
100 mm expanded polystyrene	16.00	0.06
100 mm polyurethane	25.00	0.04
One of our 125 mm (5”) walls with 100 mm polystyrene core	17.2 (approx.)	0.058
Our roof panels	25.00	0.04

R-values are a measure of thermal resistance.
U-values are a measure of thermal conductance .