Part 2: ‘Achieving the TER and TFEE Rate’. This blog focuses on the TFEE: (see related articles for parts 1-5).
It is possible under the current Part L to build a house based on limiting U-Values, get a poor air tightness result, use a relatively inefficient heating system and then pass the Target Emission Rate by using a large array of photovoltaic panels.
This approach flies in the face of what Part L is there to achieve… the objective of the regulations is to get us building dwellings which use low levels of energy. That’s not the same as a building which uses lots of energy and then compensates for the privilege.
This approach comes to an end of 6th April 2014 when the Target Fabric Energy Efficiency (TFEE) goes live. This will be familiar to some developers who have encountered the Code for Sustainable Homes – it’s known as the FEES score.
Just like with the existing Target Emission Rate, your dwelling will be compared against a notional building. You need to make sure your Design Fabric Energy Efficiency (DFEE) is lower than your TFEE.
In our previous blog, we looked at the ‘elemental recipe’. The TFEE is also calculated using parts of this recipe:
U-Values are 0.13 for all heat loss floors and roofs, 0.18 for walls, 1.4 for glazing, 1.2 for semi-glazed doors, 1.0 for solid doors and zero for party walls.
Medium thermal mass (equivalent to a cavity construction), a thermal bridging value which is better than Accredited Construction Details, but not as good as Enhanced Construction Details, and an air permeability rating of 5.
You’ll notice there are no details about heating or lighting services here, and that’s because the TFEE doesn’t consider these at all. It is purely focused on insulation levels, air tightness and good solar gains.
To allow for design flexibility, the TFEE is worked out by taking the ‘elemental recipe’ specification, and multiplying by 1.15.
The TFEE, just like the TER, is mandatory. All new domestic buildings must show compliance with both targets. (TFEE doesn’t apply where you are renovating or carrying out a change of use development).
So how do you comply with the TFEE? If you build to the Elemental Recipe, you’ll pass by 15%, so there is flexibility to make your specification worse than the recipe. Remember though: If your spec is worse in one area of the recipe, you need to make a different bit of the spec better in order to pass the TER.
If you were planning on building a house with a less-than-average specification and lots of PV, you’d pass the TER but fail the TFEE. Likewise if you were to build a house using ‘Fabric First’ techniques, and then install low performing heating systems, you could end up passing the TFEE but failing the TER.
You need to make sure you meet both targets, otherwise your building will not comply with Part L.
As you’d expect from Energist UK, our Technical Team will work with you to create a specification which complies with this new Target Fabric Energy Efficiency. If you can’t wait until April, we’ll shortly be offering consultation services using Beta SAP software – call us for details.