Cold Comfort: how can non-residential buildings deliver further carbon reductions?

Initially, heavyweight structures might appear at odds with ‘green’ design principles, yet high thermal mass systems in well insulated buildings can deliver significant carbon savings and comfortable working environments. Geoff Russell Smith, general manage of Tarmac, TermoDeck explains.

With non-domestic buildings accounting for around 100 million tons of carbon and 20 per cent of all of the UK’s carbon emissions per annum, the drive to plan, build, and ultimately manage low carbon buildings is now critical.

Making the grade

In addition to the 2006 revisions to Part L of the Building Regulations, we now stand on the cusp of new legislative power which will further impact building design, construction materials and system specification. In April 2008, the government is set to enforce the European Performance of Buildings Directive (EPBD), a major new policy document that will lead to all non-residential buildings receiving an A-G energy efficiency rating.

Under this revolutionary Directive, an energy efficiency certificate will need to be presented on construction, sale and rent of all buildings. In public buildings over 1,000 square metres, the rating will be also required to be on prominent public display.

Clearly, the EPBD will further increase the uptake of on-site renewable technology, helping proven systems such as ground source heat pumps and biomass boilers to finally move away from just being specified in one-off, best practice commercial developments.

This is welcome news. However, as well as the adoption of cost-effective on-site renewables, it is also vitally important that close attention is paid to the fabric of new buildings, because in this area significant energy efficiency gains can also be achieved.

One approach to deliveing greater energy efficiency is to incorporate high thermal mass into the initial building design. Heavyweight structures such as concrete-cored buildings have a very high thermal mass, ensuring there is a resistance to the flow of heat or conversely, ‘coolth’, through the building’s dense material. Once concrete structures reach their maximum internal temperature, the slow release of heat helps maintain comfortable room temperatures for a period of time after the initial heat input has been made.

Benefits of thermal mass

Importantly, in high thermal mass structures, external room temperature variations are not reproduced inside the building, because the maximum heat level reached during the day is delayed by the thermal mass of the building until counterbalanced by the cool of the night. This ‘thermal lag’ greatly reduces the need for further energy consumption.

The passive use of thermal mass, in conjunction with high levels of insulation, is a solid start in good building design practice. To achieve the more rigorous energy performances demanded by new legislation, a more active approach is required, such as the use of the TermoDeck system.

A concrete hollowcore solution TermoDeck exploits the high thermal mass of structural, hollowcore concrete slabs to control internal temperatures and distribute warmed or cooled fresh air through a building. The supply air passes through the hollowcore at low velocities allowing prolonged contact between the air and the slabs. In turn, this enables the concrete to behave as a passive heat exchange element that releases heat to, or absorbs heat from, the air in the slabs.

A viable alternative to air conditioning

In a well-insulated, airtight concrete building, which has good heat recovery, TermoDeck can successfully utilise the thermal mass benefits of concrete to produce an efficient environmental system. As a result, the system can replace the need for potentially inefficient refrigerant-based air conditioning systems.

The system also delivers 100 per cent fresh air with a reliability that natural ventilation cannot offer, providing an indoor atmosphere that is quiet, fresh and keeps occupants alerts – whether they be employees, students or pupils.

As energy managers are asked to meet greater energy efficiency targets, whilst cutting running costs, it is important that new building designs delivers thermally efficient structures. High thermal mass systems like TermoDeck are one such way to meet this challenge, delivering carbon savings and providing comfortable internal environments for non-residential buildings.

4 December 2007