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Get Duffy under your Toughie

Up until now, FEE has only applied to dwellings being built to the Code for Sustainable Homes. The better your score, the more efficient your building is, and the credits you can achieve in Section ENE2.

FEES is specifically designed to measure the amount of heat loss from a building (in kWh). The calculation therefore covers the quality of the building fabric only – it does not consider services such as heating, lighting or ventilation (the quality of these components will be picked up in both the SAP and the Domestic Building Compliance Guide.

Just like with emission rates, there will be a ‘Target’ Fabric Energy Efficiency and a ‘Design’. These will be known as TFEE and DFEE (pron. Toughie and Duffy).

To show compliance with Part L 2013, developers will need to make sure their design result is no higher than the target. The TFEE will vary depending on the size and envelope area of the dwelling in question, so this should mean the target is fairer than the way FEES are currently calculated under the Code. Under the CSH there are a couple of problem house types, (bungalows and flats over garages, very difficult to pick up credits) but the new way of calculating the FEE should stop this problem.

A simple way to remember this new requirement is to ensure Duffy is under your Toughie. This may come as a surprise to Duffy!

For those who are familiar with FEES, we’re expecting typical TFEE's to be around 60 for detached houses and semi’s, and around 48 for mid-terraces and flats. If you build your dwellings in line with the ‘elemental recipe’, we’d expect your DFEE to pass by around 15%, so there’s clearly some room for design flexibility in this area.

So why is this new target being brought in? The big reason is to stop builders from creating houses with minimal insulation levels, and then compensating for this by using PV panels or heat pumps.

This situation doesn’t happen very often, but when it does it goes against the first principle of Part L; which is to reduce the energy demand of our homes before adding bolt-ons.

In order to show compliance under Approved Document Part L1A 2013, all buildings must be able to show that BOTH the DER and DFEE are lower than the TER and TFEE.

Jon Ponting

Author: Jon Ponting

This article was published by Jon Ponting on 10.10.2013.