Higher thermal performance can be achieved by either installing more thermal insulation in a construction, or by using lower thermal conductivity insulation. This emphasis risks creating problems for constructions if other aspects of building codes are overlooked.
There is an opportunity for expressing the eco-thickness of architecture, but when development value puts a premium on floor space or storey heights, commercial attempts to make thinner walls and roofing are struggling with the uncertainties of product innovation. Foil-faced polyisocyanurate foams have not managed to achieve a lower than 0.021W/mK thermal conductivity. There is no full-fill polyisocyanurate foam product on the market and the reduction of air cavities in masonry walls from 50 to 25mm requires better workmanship.
Cavities behind rainscreen or ventilated coverings must be retained. Multifoil insulation products have received criticism and are now limited in their claims to performance. Silica aerogels are used in expensive internal dry-lining but cannot achieve a thermal conductivity below 0.013W/mK. It is increasingly recognised that only vacuum insulation panels (VIPs) can achieve lower than 0.005W/mK to offer the thinnest construction. Some VIPs promise thermal conductivities as low as 0.001W/mK.
Pursuit of high thermal insulation
This pursuit of high thermal insulation - whether done thickly or thinly - worries many. Pushing one of the aspects of the building regulations may be done without regard for others. A few examples are discussed below.
Compartmentation
Novel thermal insulation materials have added complexity to the fire load of buildings in ways that mineral fibre insulation used thickly does not. Agriculturally cropped insulants, recycled materials and smoke producing foams and plastics also raise issues for safety. There is a growing concern for property protection from the insurance sector.
Ventilation
Extremes of insulation performance require extremely air-tight buildings. Draughty windows are a thing of the past and glazing systems are pressure rated for air leakage. There is the fear that in designing out the infiltration and exfiltration of air, buildings will not be adequately ventilated or may have to rely on mechanical means of ventilation to avoid discomfort.
Separation
Complex detailing to achieve measurable acoustic separation between spaces is not easy to innovate. There is a market for patented products and on larger projects an acoustic consultant's advice might augment the specialisms of structural, mechanical or fire engineers. On smaller projects the architect and builder may be surprised by additional acoustic provisions.
Degradation
Products like silicones degrade and applied finishes have shorter service lives. Not enough is known about the degradation of many insulation products. Where the insulation depends on a level of vacuum being sustained it is necessary to show how performance is maintained over time, while it is often assumed that ambient air pressure fluff or foam lasts indefinitely.
Conclusion
With many thermal insulation innovations aimed at saving the energy used in building operation (and in the case of thin insulations to save space too), it is important that other aspects of building science are not neglected, or even frustrated.
Going towards thick and 'natural' insulation can be as fraught with contradictions as can trying to go to thin and industrial types of insulation. However, thinness provides opportunities for meeting performance specifications in ways that will lead to a modular discipline. Thinner high performance detailing will be easier to build.
