Achieving low carbon homes requires a fundamental rethink of many traditional construction details. They need to be re-examined in terms of their levels of insulation, thermal bridging and air-tightness. Below are further examples of construction details that architects should be aware of when building low carbon homes.
Design and Refurbishment.
In well insulated, air-tight, low carbon homes, the main use of the heating system is often to provide hot water, with space-heating as a by-product. This means that CO2 emissions associated with energy use for hot water supply will usually be more than those associated with energy use for space heating. This is the opposite of what we are used to.
Heating systems
Even very well insulated, air-tight dwellings require some form of heating system. It will be needed on exceptionally cold days, and to bring the dwelling up to temperature after and during periods with low occupation. Whilst fossil fuels are presently dominant, there are already some technologies available that have the potential to significantly reduce carbon dioxide emissions. These include
Air Tightness
It is still the case that the purpose of airtight construction is misunderstood by many architects who are concerned about health impacts. A properly designed airtight building can maintain a consistent ventilation rate in any wind, and this consistency greatly improves the air quality over 'naturally' ventilated buildings. Air tightness depends heavily on design and construction quality. The first step is to decide on the level of air tightness which can be as low as passive standards or in adherence with Part L of the building regulations.
Passive house standard - Less than 0.6 air changes per hr at 50 pa
Once the building is sealed the next step is to carry out a blower door test to evaluate the level of airtightness that has been achieved
Other Factors to consider when thinking about Air Tightness
An open fire will affect your BER. If you have good air tightness result the energy value will change significantly if you include an open flue. The open chimney can also affect the performance of your heat recovery ventilation system (HRV).
If a fireplace must be installed, an 'underfloor draught' air supply (a small duct
or pipe installed within the floor and connecting the outside air directly to the
fireplace) can help to reduce the amount of warm internal air escaping through the chimney.
A wood pellet boiler is a feasible alternative to the open fire. Wood has been used as an energy source for centuries but in recent time many homeowners are using wood pellet stoves to heat their homes due to the increase in oil and fossil fuels.
Ventilation
Once solar and internal heat gains have been reduced, adequate indoor air quality and thermal comfort can be ensured by providing natural, mechanical or mixed mode ventilation. The choice of ventilation method is often a critical component of the energy strategy for a low carbon building because it has implications for the building form, the building fabric, the building services and the way that the building should be used.
Mechanical Heat Recovery Ventilation must be provided in a well insulated house because a conventional extraction system will transfer the heat from inside to outside the house and the incoming ventilation air may be cold.
The building regulations F1 state "provide an adequate supply of fresh air for using an area or building; achieve occasional rapid ventilation for dilution of pollutants and of moisture likely to produce condensation in habitable rooms, kitchens and rooms containing sanitary appliances; and extract moisture from areas such as kitchens and bathrooms, where it is produced in significant quantities" The most efficient solution may be a Heat Recovery Ventilation unit.
The HRV System will provide a continuous supply of clean, fresh, filtered air while at the same time recovering and re-distributing heat throughout your home. It is the simplest way to save energy and breathe healthy air while reducing carbon emissions.
CPD Seminars
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please contact us.
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