Insulation Report

In order to increase the energy efficiency of construction site accommodation, the accommodation must be designed and constructed in such a way that the insulation envelope resists thermal transfer. The most basic approach that can be used for assessing the insulation envelope of a cabin is the Elemental Method. The Elemental Method involves assessing the thermal transmittance through each element of the building. The following picture shows a summary diagram that indicates the maximum U-value of the individual building elements for non-domestic buildings according to the Scottish Building Standards, Section 6 on energy efficiency.

Summary Diagram

Maximum U-values for different building elements [1]

This report recommends these values as guidance for designing an improved insulation envelope for transportable accommodation units as they are used for construction villages.

Once the U-values for the insulation envelop have been established by using the Elemental method, the following issues should be considered:

· Limiting the effect of thermal bridging at junctions and around openings that occur in the insulation envelope

Furthermore, design calculations should be carried out in order to ensure that the form and fabric does not result in excessive cooling being required for the building.

Firstly, our objective is to assess the environmental performance inside cabins conventionally used on construction sites. This report will identify how the insulation envelope of conventional cabins can be improved and to what extent heat loss can be reduced using a cabin design that reflects the current state-of-the art. Secondly, this report will demonstrate to what extent the use of well insulated site accommodation can reduce the heating demand and improve environmental comfort.

In order to improve the insulation envelope of the cabin, an insulation material with a higher thermal resistance, than the material used for insulation in the conventional design of construction site accommodation, should be chosen for the walls, floor and ceiling of the cabin. Furthermore, the thickness of insulation should be increased.

Properly designed insulation installed into walls, floor and ceiling does not only reduce the need for heating and cooling, it also provides a barrier to the entry of sound from the surrounding area. Hence, it improves the acoustic insulation and therefore creates a quieter working space.

Another benefit is the limitation of surface condensation [1], which is particularly of importance for the drying rooms of a construction village.

Changing the type of glazing is another aspect for improving the insulation envelope of the cabin.

Using air filled double glazed windows instead of single-glazed windows will reduce the thermal transmittance through the window from above 5 W/m²K down to 3 W/m²K or possibly less depending on the material used for the window frame. Ideally PVC frames should be used in order to reduce thermal transmittance.

Furthermore, cracks and openings within the building fabric have to be limited to reduce heat loss through infiltration. These infiltration losses are reduced by better seals in the construction of the cabin and by air-sealed doors and windows.

Using the ESP-r software an investigation was carried out on a typical Case Study in order to assess comfort levels and heating requirements for both a poorly and well-insulated cabin. These two types of cabin refer to designs which are both currently available on the market. In order to verify the results obtained by applying ESP-r, steady state calculations have been carried out to verify the results obtained.

Overall benefits from improving the cabin’s insulation envelope are numerous, including thermal performance, personal comfort, sound control and condensation control. Using well-insulated cabins for accommodation in construction villages provides important energy and environmental benefits.

Conventional and state-of the art cabins have the following characteristics in terms of insulation.

Conventional Cabin
	Construction ^a	U-value ^b W/m²K
Wall	· 50mm mineral wool insulation	0.67
Floor	· 60mm mineral wool insulation	0.50
Roof	· 70mm mineral wool insulation	0.54
Door	· 40mm mineral wool insulation	0.85
Window	· single glazed with aluminium frame	5.5

^a based on specification of Containex Ltd ^b U-values do not comply with the Scottish Building Regulations for limited life buildings

State-of-the Art Cabin
	Construction ^a	U-value ^b W/m²K
Wall	· 80mm mineral Polyurethane	0.35
Floor	· 100mm mineral wool insulation	0.35
Roof	· 100mm mineral wool insulation · 40mm Polyurethane sandwich panel	0.25
Door	· 40mm Polyurethane insulation	0.66
Window	· double glazed with PVC frame	2.7

^a based on specification of Containex Ltd ^b U-values do comply with the Scottish Building Regulations for limited life buildings

The following table summarises the results obtained considering energy efficiency and environmental comfort of construction villages by improving the insulation envelope of transportable accommodation used on construction sites.

	SOLUTIONS	ENERGY SAVINGS %	COST £ ^a	PAYBACK PERIOD yrs ^b	COMFORT BENEFITS
INSULATION	· Replace conventional cabins with state-of-the art cabins	60 – 70	Buy 5,000 ^c Hire 40 ^d	<22	Improved thermal comfort through: · increased dry resultant temperature · increased surface temperatures · reduced air infiltration · reduced relative humidity Improved acoustic insulation Limitation of surface condensation

^a for 9.5m ´ 3m cabin, ^b based on 10 pence per kWh energy costs ^c including VAT and transport cost; price from Lydney Containers Ltd ^d based on long-term hiring; £30 per cabin per week for conventional cabins

Wall

Floor

Roof

Door

Window

Wall

Floor

Roof

Door

Window

INSULATION