Page 15 - ZEB Final Report 2009-2017

Nano Insulation Materials for High-Performance Building Envelopes & Relective Foils in Floor and Wall Constructions | 15

Sivert Uvsløkk Birgit Risholt Jørgen Young
Senior Researcher, Research Manager, Team Leader
SINTEF SINTEF, Work package Business and Product
Leader, ZEB Development, ISOLA

Testing of relective foils in the ZEB laboratories 2016.

Relective Foils in Floor and Wall Constructions

Heat transfer through cavities can be reduced by good airtightness, by illing the
cavity with thermal insulation material, or by using relective layers to reduce heat

transfer by radiation. Air leakages can be reduced and even eliminated by layers of
airtight material such as an air and vapour barrier on the hot side of the cavity and a
wind barrier on the cold side.

The traditional solution of filling the entire cavity with some floors, a closed air cavity bonded by a reflecting foil may have a
type of thermal insulation reduces or eliminates both radiation thermal resistance equivalent to several dm of normal mineral
and convection. Air has higher thermal resistance than wool insulation. Reflective layers can also be used to insulate
mineral wool. For air-filled cavities, the thermal properties thin air cavities in walls and roofs.
can be improved by reflective surfaces which reduce radiation. A closed air cavity bonded by a reflecting foil can have a
Convection can be kept low by dividing the air space into thermal resistance equivalent to about 20 mm normal mineral
several thinner air cavities with layers of reflecting material. wool insulation in roofs and equivalent to about 30 mm in walls.
Conduction cannot be reduced in air-filled cavities since the In addition to the reduction in heat loss for floors, the
thermal conductivity of air sets a lower limit for heat transfer. temperature on the underside of the floor joists is raised by a
Reflective foils have the greatest insulation potential in few degrees during winter. The joists are then drier and less
floors where the direction of heat flow is downwards, which susceptible to fungal growth than in an uninsulated crawl space
gives thermally stable air layers and minimum convection. In with high ventilation.