Heavy electricity

SEAI recently proposed a series of changes to Deap — the software tool used to calculate BERs — including a reduction in its primary energy factor. But while this will benefit electrically-powered heating devices, some in the industry still feel systems such as heat pumps are disadvantaged by Deap and the BER system
SEAI recently proposed a series of changes to Deap — the software tool used to calculate BERs — including a reduction in its primary energy factor. But while this will benefit electrically-powered heating devices, some in the industry still feel systems such as heat pumps are disadvantaged by Deap and the BER system

SEAI is expected to lower the primary energy factor for electricity as part of a review of the Dwelling Energy Assessment procedure (Deap), the tool used to calculate BERs. The next version of Deap will also be updated to check for compliance with the proposed 2010 update to Part L of the building regulations.

SEAI proposed the changes as part of a recent review of Deap. Public consultation on the planned changes had closed when Construct Ireland went to print. The changes have yet to be confirmed, but they should be finalised in the coming months. Other alterations are also expected — these include the introduction of a method for calculating whether a combined heat & power (CHP) system is sufficient to meet Part L’s renewable energy requirement, and a mechanism for inputting the energy efficiency rating of lightbulbs. Previously Deap only distinguished between low and high energy bulbs.

The new version of Deap should also introduce alternative methods for calculating the output of domestic wind turbines. Previously turbine owners had to collect a year of on-site performance data from the turbine. But the new version should also allow users to simply input a year’s wind speed data from the site, or to calculate performance using default wind speeds.

The update to Deap proposes changing the primary energy factor from 2.7 to 2.54. The figure indicates how much energy is used in the generation and transmission of electricity from the power station to the end user — a figure of 2.54 means that for every kilowatt a building uses, 2.54kW is consumed in generation and transmission. In Deap, the primary energy factor is applied to electrical building components such as lights, mechanical ventilation systems, immersions and heat pumps.
The current figure of 2.7 has long been a point of contention among suppliers of electrically-powered heating devices such as heat pumps and mechanical ventilation systems — it dates from 2003 and hasn’t been updated since Deap was created in 2006. But the efficiency of Ireland’s electricity supply has improved considerably since 2003 as higher efficiency gas plants and more renewables have come on stream, and old peat-fired stations have closed.

Heat pump suppliers argue the delay in updating the primary energy factor unfairly penalised their machines. In Deap, the final energy the building uses is multiplied by the primary energy factors of the various fuels used (electricity, gas etc) to give the building’s primary energy demand. This figure is then used to determine whether the building meets the ‘energy performance coefficient’ (EPC) required by part L of the buildings regs — this was the 40% reduction in energy use the 2008 regs required compared to the previous (2005) standard. The higher the primary energy factor for electricity and the more electrical building components, the higher the primary energy demand and the less likely the building will comply with regulations.

The drop in primary energy factor to 2.54 will make it easier for buildings with heat pumps and other electrical heating systems to comply with the EPC, though that figure will become more onerous in the proposed 2010 revision to Part L.

The drop in primary energy factor alone is unlikely to boost the BERs of buildings with heat pumps by much, however. In a house where all space and water heating is met by a heat pump, all energy consumption is electrical. The primary energy demand in this house will fall by 6% once the new primary energy factor for electricity is introduced — the same rate as the fall from 2.7 to 2.54.

For a house with a B3 rating — the most common among new dwellings — and a primary energy demand of 135 kWh/m2/yr, inputting the new 2.54 figure wouldn’t be enough to boost the BER to a B2. But for a house that’s borderline between two ratings, it could make all the difference.

The primary energy factor should continue to drop in future as long as the government maintains its policy of modernising the grid. This means that all other things being equal, the BERs of most houses — but particularly those that are heated by heat pumps and other electrically-powered devices — would continue to improve if they were to be re-assessed regularly.

But the drop in primary energy factor won’t make it any easier for homes with heat pumps to meet the renewable energy requirement in Part L. The regulations stipulate that for heat pumps, only the energy they produce in excess of 2.5 times their electricity consumption can be counted towards the renewables requirement — the regs essentially presume that energy produced at a co-efficient of performance (COP) of 2.5 or below is offset by the inefficiency of electricity production. This indicates that the Department of Environment — which produces the building regulations — has regarded 2.5 as being a more accurate primary energy factor since the last revision to Part L in 2008.

But the 2.5 stipulation in the regs makes it impossible for many air source heat pumps to meet the renewables requirement. The default co-efficient of performance for air source heat pumps in Deap is 2.5 — if that value is used, the heat pump contributes nothing towards a  u house’s renewable energy requirement.

Heat pump manufacturers can override the defaults by registering tested performance data for use in Deap. However, this has been a point of contention in the industry for a while. Heat pump suppliers say the process of registering test data with SEAI is laborious and expensive.

To use test performance data in Deap, manufacturers must register their system on SEAI’s Harp database or use “certified data from an accredited laboratory”. The latter is necessary to get on Harp anyway, but a BER assessor may well encounter a heat pump that’s not listed on Harp but for which the right performance certs are available.

But many Irish heat pump suppliers say getting certified data from an accredited lab is a costly and unwieldy process. One supplier of ground and air source heat pumps — we’ll call him Supplier A — told Construct Ireland of his “complete frustration” after spending three years trying to get systems registered on Harp.

Various suppliers said testing and certification of heat pumps is prohibitively expensive — particularly as they are required to produce certified data from an accredited lab for every heat pump in their range they want listed on Harp. Some said this was particularly difficult considering the pace at which new products are launched.

“The cost is prohibitive,” said an air source heat pump supplier (Supplier B from here on). “The market is smaller than the capital cost of entering it, therefore there’s a market block.”

Irish suppliers point out that large European manufacturers rarely have certified data from independent accredited labs for all of their machines — they say getting it is prohibitively expensive, and that they’re not going to meet that cost just to satisfy a small market like Ireland.

SEAI do offer alternative means of compliance —manufacturers can submit data from their own labs provided it’s been certified by an approved independent body. They can also submit data for a range of products based on testing of one or two — again provided an approved lab is willing to state the sample results apply to the whole family. Another option is for a manufacturer to have their own lab accredited.

But Supplier A points out that European heat pump manufacturers are often reluctant to give up their lab facilities for long periods so approved bodies can oversee testing — it may be cheaper than sending them off for independent tests, but it’s still a time consuming exercise to satisfy the tiny Irish market. Supplier A said he would like to see a system whereby manufacturers could declare their own performance data, with SEAI or another body performing spot checks and sample tests, with penalties if data was declared falsely.

He also questioned whether getting on Harp was worth it — it might allow realistic performance data to be entered and thus help boost BERs, but he said consumers aren’t pushed about energy ratings once they know how much the system will cost to run.

The efficiency of Ireland’s electricity production has improved as older, less efficient power plants have been closed and replaced by modern gas plants and renewable energy. Dublin’s iconic Poolbeg chimneys puffed for the last time in 2010 when the site’s oil-burning electricity plant was shut
The efficiency of Ireland’s electricity production has improved as older, less efficient power plants have been closed and replaced by modern gas plants and renewable energy. Dublin’s iconic Poolbeg chimneys puffed for the last time in 2010 when the site’s oil-burning electricity plant was shut

"Whether it comes out as a B1 or B2 we don't really care because we know the running costs and that's enough for us,” he said. “Architects are looking for an A3 house, customers are not. Nobody has yet asked me before sales if our heat pump is on the Harp database.”

But Supplier B said that because conservative default data is entered in Deap for so many heat pumps, specifiers are choosing other heating systems for which they can enter actual test data, thus giving them better BERs. He said that testing of boilers is much cheaper than heat pumps, so the data needed is more readily available.

To see to what extent entering default values penalises houses with heat pumps, Construct Ireland asked BER assessor Gavin O Se to calculate how the BER of a detached two storey house varies with different heating scenarios. He did the calculations just before print, so they haven’t been double checked. The house has radiators throughout and a B2 BER. Using Deap, O Se put in a 90% efficient oil boiler as the heat source, and switched the radiators downstairs to underfloor heating (with rads still upstairs). The primary energy demand came out at 112.64 kWh/m2/yr, or a B2.

But when he changed the boiler to an air source heat pump with the default COP of 2.5 (with the heat pump contributing all space heating and half of hot water), the primary energy demand grew to 131.92kWh/m2/yr— a B3. Heat pump suppliers say this difference is driving specifiers to choose boilers — which are more likely to be listed on Harp — over heat pumps.

Gavin O Se then entered a COP of 3.8 for the heat pump, rather than the default. The primary energy demand came out at 103.92 kWh/m2/yr, still a B2, but better than with the oil boiler. When he kept this scenario but switched the whole house — upstairs and downstairs — to underfloor heating, the primary energy demand was 87.22 kWh/m2/yr, a B1.

Supplier B said the last figure raises a key point. Heat pumps work more efficiently with low temperature distribution systems like underfloor. Deap presumes that if a house has standard high temperature radiators, the water in the heating system must be heated to the high temperature they require. But Deap doesn’t distinguish between a house with one radiator and a house with a whole floor of them. It presumes the heating system in a house with underfloor throughout — but with even one towel rail heated to the same low temperature as the underfloor — is maintained at a high temperature, resulting in a 25% efficiency penalty. Supplier A called for Deap to allow users to input the relative areas of a house with different heat distribution systems.

Taking our sample house, with underfloor heating throughout and an air source pump with a certified COP of 3.8, the house gets a B1. But if the BER assessor has to enter a default COP of 2.5 for the same heat pump, and if the house has just one radiator or heated towel rail, it gets a B3.

The newly proposed revision to Deap is the first in a two stage review. The second stage will take place later this year and will focus on “wider issues relating to new and forthcoming standards along with new building design and construction methods”, according to SEAI. The organisation told Construct Ireland that in the longer term, the European EcoDesign directive will have a bearing on how heating systems are tested, and how standards are defined. A spokesperson said the directive should “result in a more consistent approach being used across Europe in evaluation of heating systems” which should “lessen the burden on manufacturers who wish to sell products in multiple countries.”