BUILDINGS Toolkit – Avoiding Heat Loss

 

Common Questions on Heat Loss and Heat Gain

 

Should I double or triple glaze?

Triple glazing contains additional embodied carbon to double glazing but saves carbon in operation by reducing heat loss. It is likely that the additional embodied carbon will be offset by the operational savings if the space that the glazing serves needs to be heated frequently for example the bar area, the entrance lobby, common spaces with large amounts of glazing, as well as the back of house offices.

In recent times, the cost uplift of triple glazing over double is circa 10 – 20%, which is likely to be recovered from the operational savings within a “medium” timeframe. One thing to note is that there may be greater size restrictions for triple-glazing due to the weight of the units. The weight is also something you should consider if retro-fitting

Should I use mechanical or natural ventilation?

For a refurbishment, the installation of a mechanical ventilation system will require a considerable amount of thought, particularly with regards to locating the associated ductwork. However, it does offer more control over the internal environment and can provide opportunity for further works for a room/building to significantly increase its airtightness. When coupled with heat recovery and the monitoring of air quality through CO2 sensors, it can be very effective at reducing carbon emissions. It is important that you seek expert advice from a professional for the vent system and also in relation to air tightness.

If there are no plans for airtightness improvements, then mechanical ventilation will not offer significant carbon savings.

For new-build extensions, mechanical ventilation can be a central part of an energy strategy as it follows the well-respected principles of PassiveHouse.

Should we introduce cooling?

Ideally, no. Consider why you might need cooling now compared to say 20 years ago as it is possible that a cooling requirement is a consequence of a build-up of internal heat gains from things like equipment, lighting or people. Can you do anything to control these?

Solar heat gain is the other factor causing overheating (which has likely not changed over the last 20 years), but external shading or roof insulation could reduce this heat gain and resolve overheating issues in the first instance.

If preventative measures are not possible and cooling is essential, then consider a VRF system (Variable Refrigerant Flow, which uses a refrigerant as the primary cooling and heating medium) or an exhaust air heat pump, that can also offer heating. This way you can simultaneously reduce the heat demand on the boiler (and any associated fossil fuels).

We want to look open, but keep warm – what should we do?

Radiant-based heating systems, such as underfloor heating, are the most effective in drafty environments as they are not primarily intended to heat the air (which then gets flushed out when the doors open).

“Air curtains” direct high jets of air behind the door to minimise the cold air ingress. These can also have heating elements, but thought should be applied to the temperature setpoints to ensure excessive heat is not wasted. It is also important to ensure that they are compatible with any future plans to reduce the heating flow temperatures.