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While the principles of low energy building apply equally for new build and upgrades, the reality is that htting passive levels becomes much trickier when retrofitting. The Passive House Institute have taken this on board and created a retrofit standard that is ambitious but achievable.

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Official magazine of EascaEasca
EnerPHit E-mail
Wednesday, 01 February 2012

Dormer bungalow refurb, Rathdrum, Co Wicklow

Randy Ralston and Mel Cronin were about a third of the way through the refurbishment of their 1970s dormer bungalow in Rathdrum when they decided that they would try for passive. They began their project before EnerPHit was established, which meant that trying for passive involved aiming for the Passive House Institute’s exacting new build targets – annual heating demand no higher than 15 Kwh/m2/yr and airtightness of under 0.6 ACH. Though they just missed these targets, the project remains an exceptional refurb. A heat energy load of 17.9 kWh/m2/yr and an air change rate of 0.92 ACH comes well within EnerPHit parameters. Moreover, the addition of renewable technologies including a wind turbine and PV panels mean that the house, which was featured previously in Construct Ireland, is actually a net energy contributor, with a BER rating well in excess of the A1 threshold. Earlier this year, the project was a runner up in the Isover Energy Efficiency awards.

Achieving airtightness is one of the biggest challenges faced in a passive refurb.  A rate of 0.92 ACH took a huge effort.  "It's true we did get a bit carried away with ourselves when we realised that actually going full passive seemed within our grasp," Ralston told Construct Ireland in September 2010. "At one point we completely downed tools and spent two weeks with a team of six people doing nothing but searching for and sealing air leaks using the blower door, air pens, smoke machines and even incense." 

Dormer bungalow refurb, Rathdrum, Co Wicklow

"We invented ways of sealing the recessed lighting using silicone rings, and used gargantuan amounts of fireproof acoustic mastic." He said. "We even had representatives from the various airtightness materials manufacturers visit the site during that time to advise us how we could improve and they could offer nothing, saying we were doing ‘everything right’”.

Selected project details

Clients: Randy Ralston & Mel Cronin
Architectural & passive house consultant: Archie O’Donnell
BER assessment: Energy Matters
M&E: Robert Hassey Electrical Ltd
External insulation: Aerobord
Service cavity insulation: Rockwool
Cavity wall insulation: Warmfill
Blown cellulose insulation: Ecocel
Insulated foundation system: Viking House
Windows & doors: Ecoglaze Ireland
Roof windows: Tradecraft
Airtightness products and Gutex insulation: Ecological Building Systems
OSB board: Smartply
Solar evacuated tubes, air-source heat pump & buffer tank: C-MC Energy
Rainwater harvesting: Rainharvesting Ireland
Wind turbine: Sunstream Energy
Solar PV & Emma controller: Coolpower
Heat recovery ventilation: MTD Solutions

Project overview:

Building type
: 1970s detached two-storey house gutted and extended to 339 square metre house

: Rathdrum, Co Wicklow

Completion date
: December 2010

Space heating demand (PHPP)

Heat load (PHPP)
: 12w/m2

0.92 air changes per hour

EnerPHit certification
: pending

: Upgraded from an F to an A1 rating

Ground floor
: existing concrete floors dug out and Viking House insulated foundations installed with 300mm of EPS.
U-value: 0.12 W/m2K

Extension walls
: timber frame walls – 140mm & 90mm twin-wall studs filled with cellulose, with 15mm of pro clima tapes sealed to OSB inside & outside, 200mm of EPS insulation externally & a 100mm Rockwool-filled service cavity internally lined with Intello vapour check & Fermacell board.
U-value: 0.11 W/m2K.

Original house walls
: the cavity walls were pump-filled with bonded-bead & externally insulated with 200mm of EPS, then lined internally with Intello vapour check, followed by Fermacell board.
U-value: 0.14 W/m2K

Extension flat roof
:150mm EPS insulation under a fibreglass roof membrane, followed underneath by a plywood deck, nine inches of cellulose insulation, taped & sealed OSB as vapour control layer, & 100mm of Rockwool in the service cavity below.
U-value: 0.13 W/m2K

Existing roof: 60mm of Gutex soft board placed under the roof tiles, cellulose insulation between the rafters & a 100mm Rockwool-insulated service cavity underneath. U–value: 0.13 W/m2K

: triple-glazed Internorm windows replaced single glazing throughout. Edition & Edition 4 models were specified — the latter includes a controllable blind between the triple-glazing & a fourth separate outer pane. Both models are timber alu-clad with argon fill.
The Edition units have a U-value of 0.86 W/m2K overall, while the Edition 4 has an overall U-value of 0.8 W/m2K with the blinds rolled & 0.7 W/m2K unrolled

Roof lights
: timber-aluclad, krypton-filled Fakro units.
Overall U-value: 0.94 W/m2K

Heating system
: 120 solar evacuated tubes meet 70% of domestic hot water requirements & supply underfloor heating, backed up by an Emmeti air-to-water heat pump with a COP of up to 4.49 based on Eurovent conditions (air in at 7/6C, water out at 30/35C). Hot water is stored in a three coil Akvaterm 2,000L insulated tank.
U-value: 0.22 W/m2K

: MTD ERV 500 heat recovery ventilation system

Green materials: cellulose insulation, Gutex soft board

Electricity:  a 2.9kW solar PV array consisting of 14 Sanyo HIT panels & EMMA controller paired with a Skystream 3.7 wind turbine rated at 2.4 KW in wind speeds of 12 metres per second (m/s), equivalent to 27mph


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