Andrew Lundberg on Ireland’s nZEB Opportunity

There are changes afoot in the European requirements for energy performance of buildings. These don’t come in the form of some wishy-washy broad sweeping statements, but will whittle down to the literal nuts and bolts of how we put our buildings together right here in Ireland. So to put it simply, everyone will be affected, from designers, specifiers, products suppliers and contractors down to the occupants themselves, who will benefit from new buildings of a quality seen only by Passive House dwellers to date. At least that’s the opportunity that lies before us if we do it right.

You could look on these new upcoming changes, brought in under the Energy Performance of Buildings Directive (EPBD) 2010 – recast, and translated into something we can really get our teeth into in the form of the new upcoming Technical Guidance Documents Part L (for both dwellings and buildings other than dwellings) as a further restriction to design, more box ticking, more calculations, complexity and cost. Or you could see it for what it really is….opportunity.

The EPBD in itself is straightforward in that it doesn’t set target values as such. It merely says we should have a national calculation methodology for measuring building performance in terms of Primary Energy Consumption (kWh/m².annum) and Carbon emissions (kgCO₂/m².annum), and that our buildings should be designed to the nearly-zero energy building (nZEB) standard and in a cost-optimal way. It loosely defines an nZEB as a building which has a very high energy performance value, and whereby a significant portion of that required energy is provided by renewable energy resources on-site or nearby. What it also says however, is that space heating & cooling demands should be brought to optimal levels before looking at alternative energy resources. In other words, design a building that needs very little, and then you’ll have little to do in worrying about how you’re going to provide that energy in the first place. The fabric-first approach. The right approach.

There are many arguments for the fabric-first approach. The problem is, these aren’t always immediately obvious at the time of design/construction, but only become obvious once a lifecycle cost assessment of a project is carried out. This is something we need to be doing more of on a project-by-project basis. After all, the life expectancy of a building normally far outweighs the service life of the plant that heats, cools, lights and ventilates it. By using the fabric-first approach, a lot of cost and hassle issues associated with plant can be reduced or even eliminated. After all, when’s the last time you called a technician to service your attic insulation? Or change a component in your floor insulation due to a fault?

There are also however issues inherent to the national calculation methodology, also know as the DEAP (Dwelling Energy Assessment Procedure) method used to determine a building’s BER rating, and forming a large part of compliance with Part L of the Building Regulations, which mean we are more often-than-not designing buildings in a wasteful fashion, ultimately costing more money to build, which is naturally passed on to the consumer. Thank God we don’t have a housing crisis then to further exacerbate this problem (end of sarcasm).

There are numerous default values used in the DEAP assessment which are in most cases far more onerous than the building’s true performance. This is especially true of standard housing designs typical of most developments in this country. Let’s be clear on something. Demonstrating compliance using DEAP is very much a numbers game. You are up against an opponent in the form of the 2005 reference dwelling. Fair enough, its performance values are quite poor compared to what we’re used to these days, but then again, ultimately you have to perform 60% better than it under current Part L (2011) Dwellings, and under nZEB will be expected to perform 70% better in energy performance. The current requirement is with us six years, and let’s be honest, we still don’t know how to beat it in every case, even though we should. The nZEB requirement is not just peeking around the corner, it’s staring us straight in the face. This means there is no room for complacency on any single aspect of design, everything must be optimal.

One key area dear to my own heart is the accounting for thermal bridging under DEAP. The current method allows for the use of a thermal bridging, or Y-factor, value of 0.08W/m²K when building in accordance with the Acceptable Construction Details (ACD’s), or the use of a Y-factor of 0.15W/m²K when thermal bridging basically hasn’t been looked at in the design, albeit all with the inherent assumption that all details have been examined by a competent professional and deemed to be free of any condensation risk both interstitial and surface. Looking at those numbers in some context now, we can see firstly that the units are the same of those of a U-value, in W/m²K. This is handy, as it allows direct comparison of the two, as they both look at heat loss from the building as a function of the building’s exposed envelope area. If you take a building with an average area-weighted U-value of 0.20W/m²K, and use a Y-factor of 0.15W/m²K in DEAP, what you are literally saying is that 43% of fabric heat loss is due to thermal bridging. This is a gross over-statement in the context of most housing developments. Building to the ACD’s and assigning the 0.08W/m²K value means a proportion of 29% fabric heat loss from thermal bridging. Better than the previous example, but still generally unrealistic. What’s the big deal? Well, back to our numbers game. Anywhere that performance suffers either due to the use of poor product or design, or indeed use of onerous default values in the assessment, will need to be compensated for by improved performance in other aspects of the design. The bottom line is that this costs money. That is unavoidable, and unnecessary.

With correct detailing of junctions, using materials produced within our own borders, it is very possible to achieve heat loss from thermal bridging on the order of 10-15% of fabric heat loss, which would be the equivalent of Y-factors of 0.015 – 0.025W/m²K. Not only does this produce a superior building for the occupants, it can also save much more than it costs. One company demonstrating this with their range of aerated autoclaved concrete blocks is Quinn Building Products. Quinn have a range of three light-weight blocks, namely B3, B5 and B7 named in accordance with their respective compressive strengths, which can meet structural requirements to satisfy Part A (Structure) as well as having thermal conductivity values ranging from 0.12 to 0.19W/mK. When compared with the thermal conductivity of standard medium density blocks at 1.33W/mK, it becomes obvious that placing a Quinn Lite block at the right location, i.e. where the greatest risk of thermal bridging occurs at junctions, can greatly reduce heat loss at the junctions, as well as increasing surface temperatures thereby greatly reducing risk of mould growth and improving occupant comfort.

One issue which always surfaces during these kinds of discussions is the availability of resources. Let’s be honest, there are so many products now available as construction systems, or individual components for improving build speed, quality, safety or prevention of heat loss, that it would be impossible for any public body to produce a catalogue outlining their uses and thermal performance. If we’re going to achieve the nZEB standard, it is up to these product suppliers to demonstrate what their products can do, and produce certified data to back it up. Quinn have a freely-available on-line catalogue of certified construction details which include certified thermal bridging values, both psi-values for energy and fRsi values for surface condensation compliance, with c. 5,000 individual values calculated. This catalogue can be used to calculate Y-factors for entry to DEAP at no cost whatsoever. The savings that can be enjoyed from this simple exercise can run into the thousands of euros on one-off projects, and at scale those figures can be become quite significant.

The nZEB standard is going to significantly affect both the domestic and non-domestic building sector. If we’re going to achieve it, we have to understand it. This coming November 15^th and 16^th will see the World nZEB Forum take place in Clayton White’s Conference Hotel, Wexford Town, with Quinn Building Products as the main sponsor of the event. The exhibition area is filled by product suppliers showing their latest innovations and solutions to the nZEB requirement. Quinn Building Products will be showcasing a new previously-unseen innovation designed to make nZEB design and construction much easier.

The forum will provide insight into the requirements of the upcoming regulations, with Sean Armstrong, Building Standards, Dept. of Housing, Planning & Local Government, to present the freshly-published Technical Guidance Document Part L (2017) Buildings other than Dwellings. Ciaran O’Connor, State Architect (OPW) will also showcase the exciting work being done here in Ireland at nZEB level. Award-winning Project Manager Rob Fox, formerly of Walls Construction, will present on the Dublin Landings Project and the challenges faced by contractors on large-scale projects to achieve compliance with high energy performance targets. Deborah Moelis, Project Manager of the world’s tallest certified Passive House building (26 storey Cornell University Tower), Scott Foster, Director of Sustainability, United Nations, and renowned sustainable architect Jay Stuart are among some of the top-level industry and community speakers who will be presenting. This is an event not to be missed, and promises to provide a forum for learning, discussion, collaboration and seeing beneath the surface of how low-energy buildings are designed and built in the real world.

In addition to this, the previous day consists of a half-day series of workshops being hosted by Wexford County Council at the county buildings, which will include demonstrations on achieving air-tightness, thermography of buildings, and live building of a 3D thermal model of a building junction. This is open to all ticket-holders. The gala dinner on the evening of the 15^th will be attended by the Minister for Housing Eoghan Murphy, with other key delegates to speak including Quinn Building Products Chief Operations Officer, Kevin Lunney. This is an exclusive event so anyone wishing to attend is advised to book early. We look forward to seeing you there.

• Andrew Lundberg

  Jason Martin is the Specification and Product Development Manager at Mannok. Much of his daily focus is on...

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