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Wednesday, 2014-07-23
Passive houses
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Passive House Institute information on passive houses

Passive rooftruss lifted in position. Hibernia 138 with 35 degree roof and attic conversion.

Passive house in Darmstadt, Germany
Visit the Tawnylust website
Nordica 146, passive, 30 degree roof pitch, nordic exterior timber boards, partially converted into a B&B (Tawnylust Lodge)

Hibernia 138, passive, with converted attic and 35 degree roof pitch

Nordica 94, passive, reduced roof overhang and 30 degree roof pitch

Nordica 125, passive, with converted attic and 40 degree roof pitch

ESB electricity usage passive house galway

Further improvements of the standard low-energy house from Scandinavian Homes Ltd can be done to various degrees. This page will present an upgrade package that turns the standard Scandinavian Homes house into a Passive House. We will use this term in the following text. This type of house can also be called:
  • Passive-house
  • Zero-energy house
  • Body-heat house
  • House without heating

CEPHEUS Cost Efficient Passive Houses as EUropean Standard. This EU project is part of the THERMIE programme. The definition of a PASSIVE HOUSE used by CEPHEUS can be used: (You will find more information on: www.cepheus.de)
"Passive Houses are buildings which ensure a comfortable indoor climate in summer and in winter without needing a conventional heating system. To permit this, it is essential that the building's annual demand for space heating does not exceed 15 kWh/m2year. The minimal heat requirement can be supplied by heating the supply air in the ventilation system - a system that is necessary in any case.

The standard has been named "Passive House" because the passive heat inputs delivered externally by solar irradiation through the windows and provided internally by the heat emissions of appliances and occupants essentially suffice to keep the building at comfortable indoor temperatures throughout the heating period. It is a part of the Passive House philosophy that efficient technologies are also used to minimize the other sources of energy consumption in the building, notably electricity for household appliances. The target of the CEPHEUS project is to keep the total final energy demand for space heating, domestic hot water and household appliances below 42 kWh/m2year".

The criteria for a Passive House per m² living area:

  • Max. 10 W/m² constant heating-load
  • Max. 15 kWh/(m²a) annual space-heat requirement
  • Max. 42 kWh/(m2a) annual total amount of active energy input
    Max. 120 kWh/(m2a) total energy requirement for space-heating, domestic hot water and household appliances

HOW TO BUILD A PASSIVE HOUSE:

Never having to spend money on heating the house is a very attractive concept. To reach this very high level of performance one could expect that the building costs would increase sharply. This does not have to be the case. The costs are not excessive as long as the design and orientation of the house are carefully considered. Some general points about design:

  • Consider a bulky shape with minimal surface area.
  • Large windows to south - none to north.
  • As few external doors as possible.
  • One roof-half in direction true south for solar collectors.
  • Consider building a single-storey house.
  • Consider building a duplex with two or more apartments in one body.

The building procedure would be much the same as for any Scandinavian Homes house. The foundation with all insulation is done by us. The shell with triple glazing and felted roof is made by us. The only difference is that the added 70mm of studs and insulation in the external walls would have to be done by your local finishing carpenter and the cellulose fiber insulation contractor.

Please contact us to develop your ideas. Generally, any single storey Baltica, Nordica or Hibernia house would be suitable. The compact shape of a true two-storey house provides a good bulky shape with minimal surface area. All the two storey types in the Uppsala, Kalmar, Stockholm and Dublin lines are suitable. When two-storey designs are to be built to passive standard the challenge is to make it airtight. It is much more demanding for the finishing team compared to build a single storey version.

Download and view our standard Sections for passive houses and super passive houses here. (click on image to open/download)

 

 

 

 



UPGRADING THE STANDARD SCANDINAVIAN HOMES LTD HOUSE TO A PASSIVE HOUSE:

The standard low-energy Scandinavian Homes Ltd house can be improved to become a passive house. Many of the prerequisites of a Passive house are already in place with our standard models. First and foremost the house must be airtight and so one must start by designing a house that can realistically be made airtight i.e. design something that the local builder can make airtight with the skills and materials available to him. It is easy to sit in an office and fantasise about fancy designs, it is another matter to make it happen in the field. For this reason many of the passive houses currently being built by Scandinavian Homes are single story designs. This makes it easy for the local builder to succeed with the airtight membranes. Another huge advantage is that it costs relatively little to upgrade any single storey Scandinavian Homes house to full passive standard.

The following listing explains the upgrade:

Passive solar gain: The passive gain of incoming solar heat through the windows will cover close to 40% of the heat losses if all guidelines are followed. Optimised south facing glazing with none or minimal window openings to the north is a requisite. Most windows should be fixed as these have a higher performance than the opening type.


Göteborg-Lindås passivehouse by : Hans Eek / EFEM Arkitektbyrå

Windows: The standard triple glazing with one low emission shield and argon fill has a glazing U-value of 1.0. Taking into account the heavy timber frame, the average U-value for an openable 12-12 sized window is 1.2 W/m2C°. In the Tooreeny passive house we used upgraded triple glazed windows with double LE shields and double argon filled cavity as well as warm edge glazing-profile. We notice a little loss of light-transmission and a slight brown tinting of the light due to the second layer of LE coating. For this reason, and the fact that it cost a little more, we ship the regular triple glazed windows with single LE shield and single argon fill in both “low-energy houses” as well as “passive-houses”.

External doors: The standard door has a U-value of 1.0 W/m2C°. This can be improved by adding an extra internal door swinging into the room. Otherwise doors with U-value of 0.8 W/m2C° must be sourced. As with all components making up a passive house, the total performance of the house must be considered. A large house with many doors will have much larger heart-losses and this must be compensated by significant improvement of all components. In many well designed houses of moderate size, the standard door is sufficient to meet the passive criteria.

Wall: The standard wall insulation consists of 145mm of semi rigid Rockwool insulation carefully fitted between 45x145mm studs spaced 600mm apart with minimized cold bridging. The U-value is 0.25 W/m2C° using Swedish calculation methods. The value using British Standard sounds a lot better; 0.20 W/m2C°. Please observe that in the following text we use the Swedish method

Upgrade A; For most houses that are designed with passive performance in mind it is sufficient with a minor upgrade. Simple composite studs made up with 45x45mm studs and 25mm aero board and regular 45x70mm studs are added to the inside of the completed shell. 70mm of additional Rockwool gives a total insulation thickness of 215mm The vapour barrier is already installed in the factory. The U-value of this optimised wall is 0.16 W/m2C° (Swedish calculation method)

Upgrade B; For large and demanding houses. An additional layer of 120mm Rock wool is added between the standard wall and the 70mm upgrade. This gives a total insulation thickness of 335mm The vapour barrier has to be installed on-site. The U-value of this super-wall is 0.10 W/m2C° (Swedish calculation method) This is how our Tooreeny Hibernia 164 was built. In retrospect it was overdone. According to the Passive Haus Institute calculation program, the house requires a constant heat load of 4 W/m2 when the requirement is only less than 10 W/m2.

Roof: Single storey houses. This is the ideal situation when building to fully passive specification. Simple and cheap. Cellulose-fiber insulation is blown to a thickness of 500mm over the entire ceiling. U-value 0.066 W/m2C°
Houses with attic conversion. The thick roof takes away too much headroom except in the widest house type with increased roof pitch. The need for perfect air tightness is more difficult to achieve in practice with an attic-roof truss. We have developed ways to do this but it is essential the finishing team are willing to work to the exact specifications and with the tools required. The passive upgrade consists of: special cold-bridge free roof truss without vertical enforcements. The space for insulation within the truss is 400mm on the sloping part, 500mm on the horizontal part on top. The vapour barrier is installed in a special way to make it connect to the vapour barrier in the walls on the ground floor. U-value 0.082 W/m2C°

Floor: The standard base unit provides good insulation of the circumference of the foundation.
Upgrade: We add another 60mm of polyurethane insulation on the inside of the base unit and the 120mm of expanded polystyrene under the house is increased to 280mm. U-value 0.1 W/m2C°

Air tightness: The entire building envelope must be totally airtight. The vapour barrier must be overlapping 500mm and sealed everywhere. All windows and doors must meet the required air-leakage standards. < 0.6 air changes /h at n50. One experience of the CEPHEUS project is that the total energy performance of a passive house is, to a large degree, dependent on how airtight the house is. Another reason for why this is of paramount importance is the risk for condensation within the wall. The temperatures within the outer layers of a super-insulated wall are quite low. If moist warm air from the interior migrates into the wall the dew point will be met and condensation will happen in the insulation.
Upgrade: Our standard age-proof 1200g/m2 vapour barrier is taped with a special double tacky strip on all joints. The special details where the roof meets the wall is covered in the instruction manual.

Ventilation: The Temovex ventilation heat-recovery system can be set to slightly lower speed for a passive house. The ventilation system for a standard Scandinavian Homes Ltd. House is designed for a 0.5 air-exchange per hour. In the passive house the recommendation is to lower this to 0.3 exch/h. The requirements are: minimum 80% transfer efficiency in the heat exchanger and 30m3 extraction air per hour and person in the house. All ventilation ducts must be insulated. The blown-in insulation in the attic covers ducts up to dia 160mm.
Upgrade: not necessary

Tap water: Around 60-70% of the hot water required for a house can be got from solar collectors on the roof. This is only possible when one half of the roof is oriented to south. This southern orientation is possibly a requisite for a passive house. A large accumulation tank of circa 500 liter with a built in electrical heater for topping up is required.
Upgrade: solar collectors, accumulation tank and controls

Cold bridging: Building element junctions: A complete thermal bridge free construction is needed. In the CEPHEUS project the linear thermal transmittance to exterior must be below 0.01W/mK°
One drawback with the super-insulated wall is the loss of floor area. A standard Nordica 125 has an internal floor area of 8.6m x 14.4m = 125m2 In the passive version the same size house has a floor area of 121m2. This means a loss of 3,3% of the internal floor area.
Another important part of the passive house concept is that the shape of the house should be optimal. The consequence of this is that only compact bodies should be used.
The domestic electric usage must also be reduced by installing the most energy efficient models of appliances available and also low energy lighning. In the passive Toreeny house we use modern high frequency fluorescents with soft and flicker free light.


20 terraced houses without heating systems. Located in Lindås, Gothenburg, Sweden. By Hans Eek / EFEM Arkitektbyrå Göteborg


Super passive Hibernia 164 with solar collectors for domestic hot water on the south-sloping roof

Other links and resources of interest:
Swedish Passive House Centre
Passive house institute in Germany (Passivhausinstitut)
Conference on passive houses (Passivhaustagung)
Swedish energy agency (Energimyndigheten)
IEA solar heating & cooling programme, task 28
Cost Efficient Passive Houses as European Standard (cepheus.de)

Some of our suppliers:
Windows (NorDan)
Internal doors (GK door AB)
Mixer taps (FM Mattsson)
WC (Ifö)
Wall Insulation (Paroc AB)
Cellulosefiber insulation: Warmcel
Stoves: Jydepejsen A/S
Timber products: Siljan timber

We also like to present some competitors:
Irish passive house heavy-construction
German passive house manufacturer
German passive house designer
Passive window manufacturer
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