I recently completed a course run in conjunction with the RIAI and Building Life consultancy on the topic of low energy retro fits within the domestic market. As A BER Assessor I found it extremely interesting to see the areas of energy design that did not feature in a BER certificate. The Use of the DEAP software for design purposes was made clear and is a valuable tool going forward in designing for the future builds. The main area of concern within the course was the treatment of the Thermal Bridging of a building both in its existing state by DEAP or in a future design assessment for Architects and clients. Over insulating walls and bad or improper detailing of new insulation can lead to increased risk of wall failure. Not dealing with the Thermal bridging effect when insulating an existing wall can exasperate the condensation issue at window cills and corners. Building Ventilation must be addressed within a retro fit design when improving airtightness and insulation factors. Not assessing these issues will result in wall failure.
Warning - Some insulating companies offer a service to clients which provide the insulation to the external or internal walls. Not assessing the impact on the existing house and use can in time lead to mold and general insulation failure of the wall. Contractors are then long gone and the remedial work required to rectify the damage can be very costly. Nobody wants to spend more money than they have to, however the bigger picture is that it is better to be advised as to how much you should spend before the works commence rather than an ongoing shopping list of problem solvers.
New Regulations are due to be published for part L soon and we would all urge the department to look closely at some of their tables, and standards which are now outdated and to take the opportunity to help us all move forward with details and designs that we know will work in Irish conditions.

A draft version of the new TGD L(2010) is currently on Public Consultation, which is aimed to achieve 60% reduction on energy consumption from 2005 standards.

Part L

It has good points but many weak areas:

  • In general this document does not represent a good transition point on the way between TGD L(2005) & TGD L(2013), given that the latter will be 70% more onerous than the last Regs under which this Industry built many dwellings.
  • There is still far too little guidance on retrofit. This is still predominantly a new-build guidance document, despite the fact that the retrofit market is dominating domestic construction at the moment.
  • Compliance is measured against a ‘Reference Dwelling’ being linked to geometry and perimeter/area ratio. This makes it harder to comply for dwellings with more compact envelopes which is inappropriate.
  • There is no minimum airtightness standard for new extensions.
  • For internally insulated walls, there is no understanding of the fact that low (i.e. ‘good’) U-values are linked to higher risk of unacceptable levels of inter-stitial condensation
  • Also, the Glaser method is given as the normal method of assessing inter-stitial condensation, with hygrothermal simulation listed as an option. In fact, hygrothermal simulation is the ONLY assessment method suitable for heavyweight structures (e.g. drylined hollow block).
  • It is increasingly clear that U-values for walls should be differentiated into those suitable for internal insulation, cavity wall insulation and external wall insulation. We believe we’ve already exceeded the limits of sensible values for internal wall insulation, but there is further room for better cavity and external U-values. It’s crazy that only one value is given.
  • We suggest that because U-values lower (i.e. better) than 0.50 W/m²K
    are increasingly risky for internal insulation, it no longer be an acceptable choice for new build dwellings in TGD L (2010), which currently requires performances of 0.21 W/m²K or better for new-build walls.  Obviously as with other ways of building considered to be outside the usual, dependable norm the specifier could continue to use that system IF they were prepared to prove how it makes sense in their exceptional circumstance.  We suggest internal insulation would remain in use for retrofit work with the lower limit of 0.50 W/m²K  suggested.
  • Designers no longer need, nor should be allowed, to use 0.08 W/m²K as a default value for a Y-factor when using ACDs, given the creation of Tables D1-D5. In doing this we would be following what has just happened in the UK. It will now be easy to calculate a much more accurate Y-factor for dwellings that comply with ACDs using these tables. ACDs should also be expanded to allow for a Y-factor of 0.04 W/m²K to help compliance in new build
  • The default thermal bridging Y-factor of 0.15 W/m²K is too generous for retrofit, values can be many times worse. We suggest 0.25 W/m²K is a more realistic default value for retrofit. A default Y-factor of 0.15 W/m²K does appear to be reasonable for new dwellings that don’t comply with ACDs and uninsulated existing dwellings
  • Given the jump in regulations we are seeing, dwellings which exceed the requirements for compliance by, let’s say more than one energy rating, should have a lower, or no, renewables obligation. They’re spending the money in the right place: on the fabric. Equally, the current situation where even more renewables can be used to ensure compliance of a building with large perimeter or non-optimised fabric, is like a ‘back door’ approach that is neither sustainable nor economic long-term.

Adding value to a home must include a design which will allow for cheaper fuel bills, and healthier living conditions and better ventilation. It is Project Designs Architects view that all these must be incorporated into good retro fit and new build designs projects alike and if necessary the client may need additional time to help understand the process and the terminology used to arrive at a successful end project. Yesterdays big world economics is gone and today people need their Architect to take the time to help clients think about life standards, healthily homes, low energy usage, commuting, energy source, which will then start to make some sense of recycling of bottles and green waste management on domestic levels.

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