Home improvement & energy retrofit
Home improvement through extensions and renovations can give you more space, make your home more valuable and improve your quality of life. Taking steps to enhance the energy efficiency of your property at the same time can make your home warmer, more comfortable, healthier and reduce your energy bills.
There is a lot of information available about various efficiency improvements you can make to your home, for example on the Energy Saving Trust website. However, to make an energy efficiency retrofit project successful you need an understanding of the house as a whole and an overall strategy.
Using a case study of a current live project, this post is the first in a series that will take you through a retrofit project from the early stages all the way through to completion on site and post-completion evaluation.
Step 1 : Assessing the existing building
Our case study project is a semi-detached cottage style property located in a south Nottinghamshire village. The first thing to establish about the property is the approximate construction date as this will give an indication as to probable materials and construction methods. This property was likely constructed in the early post-war period and has an extension to the rear which was known to have been constructed in 2008.
Next we need to look in detail at the different elements that make up the building’s ‘thermal envelope’. The thermal envelope refers to the floors, walls, windows, doors and roof that together provide shelter from, and interaction with, the external environment. This is the most important part to address in any energy retrofit project. This approach is called a ‘fabric first’ approach to energy retrofit and ensures that the fundamentals are addressed prior to any investment in technological solutions.
Taking each element in turn we can make the following assessment:
- Roof insulation: there is a thin layer of existing roof insulation but this is insufficient to provide adequate protection against heat loss through the roof.
- Windows: existing replacement uPVC glazing is old and has lost its vacuum, meaning it is not functioning as intended.
- External doors: the existing uPVC doors appear to be well sealed and fit well.
- External walls: prior investigation into the wall construction revealed that although a narrow cavity is present in the walls it is not suitable for cavity wall insulation.
- Ground floors: uninsulated solid concrete floors.
To the rear of the property is a single storey extension built in 2008 and a conservatory. The requirements of the building regulations in 2008 mean that the extension would have been constructed to higher energy efficiency standards than the rest of the house. The conservatory however has the potential to contribute to high heat loss if not used as intended. Conservatories should only be used in shoulder seasons when the external temperature is neither too hot nor too cold and they should never be artificially heated or cooled.
Step 2: Developing a retrofit strategy
From our analysis we can now move on to developing an overall strategy for the energy retrofit. The development of the strategy will be influenced by the effectiveness, cost and practicality of each individual measure in relation to others, along with overall budget for the project. Deep retrofit projects can result in a home with remarkable energy efficiency credentials (e.g. PassivHaus standard) but require larger budgets and more significant upheaval to the existing property, lighter touch retrofit projects can still bring many benefits at a lower capital cost and with less disruption.
The strategy chosen for our case study project is a relatively light touch retrofit, working with the existing building to improve the thermal envelope and reduce overall heating demand but retaining the existing means of ventilation (natural ventilation and controlled trickle ventilation) and existing gas fired central heating boiler. The key areas to be targeted in the strategy are as follows:
- Roof insulation: upgrade the existing insulation, increasing the thickness to the recommended minimum of 270mm.
- Windows: existing windows to be replaced with new gas filled, thermally broken, double glazed units with trickle vents.
- External walls: breathable internal wall insulation to be installed to the inner face of existing external walls.
- Conversion of conservatory: existing conservatory roof and existing glazing to be removed, external wall to be insulated internally and new fully insulated roof to be added.
Making the most of architectural opportunity
In addition to the energy efficiency measures described above, the opportunity to make architectural interventions to improve space, increase value and enhance quality of life must not be forgotten. This project will also see the addition of a front porch, both an aesthetic and energy efficiency improvement (providing an air lock between the external and internal environments), along with a reworking of the rear elevation to improve the overall appearance. Energy efficiency improvements go hand in hand with architectural improvements and one cannot be thought of as separate from the other. Look out for our upcoming post ‘Energy Retrofit Your Home 2’ which explores these improvements in more detail.