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George Street, Cellardyke, Fife

George Street, Cellardyke, Fife

Benefits and options for the retrofit of an 18th century traditional Scottish house using the Passive House Standard

Overview

The aim of this case study is to create an outline of the barriers and advantages to the integration of the Passive House standard for the future retrofit of the dwelling in Cellardyke, Fife.

The main objectives of the case study are:

  • To analyse the current state of the home and look at the main elements to retrofit.
  • To consider all the targets that are set by the Passive House standard.
  • To guide the owner and architect on the areas which will need to be upgraded and to what level. 
  • To facilitate the architect on how to achieve the standard and the loopholes which surround it.

Approach

Existing fabric

The dwelling is a two storeys high stone walled, timber structure, 18th C town house with a converted attic space with limited head space between rafters and joists.

The main elevation is finished with rustic cement render applied onto a single core sand stone wall. All lintels and sills are flush with this render which gives the impression that it isn’t original and was applied latterly. The front windows have been upgraded to recent PVC framed double glazed units. The roof has a double fall to the rear and to the front elevations. A dormer window dominated the front elevation belonging to the converted roof space.

The back elevation has partially preserved its original sand stone lime pointed finish, the right hand side of the external wall has a lime render. The distinctive feature of this elevation is that it has a semi-circular stone extruded stair case from ground floor to first floor. The windows are also recent PVC double glazed units which stand out from the original features of the building. Two skylights appear on the roof that open in to the converted loft space.

The roof is timber structured with higher than usual timber joist. Additional ceiling joist underneath are also present which support the voids floor. Externally it is covered by traditional terracotta clay pan-tile typical of the region. 

 

George st Front portrait SEC_300X185

Image: Front of case study dwelling at George St, Cellardyke, Fife

George st rear SEC_300X280

Image: Rear of case study dwelling at George St, Cellardyke, Fife

 

Passive House retrofit 

A passive house or “Quality Approved Passive House” is a house that is regarded as energy-efficient and benefiting from an all year-round comfort and good indoor climate without the use of active space heating or cooling systems. The space heating requirement is reduced considerably by using passive measures integrated to the building fabric or as building methods that can use natural means of heating and cooling. The objective is that with adequate use of passive solar and ventilation methods in combination with internal gains, that an all year round comfort level is reached with minimal energy use.

During design stage and specification, the use of various criterions is applied. The standard relies on the use of its Passive House Planning Package (PHPP) which helps the designer to verify and properly specify the passive house. According to the Scottish Passive House centre “It has proven itself over many years as a reliable and accurate instrument for energy balance calculations and for the implementation of design changes in order to improve energy balances on domestic and commercial buildings”

The homes are regarded as being highly insulated with minimal thermal bridging around the fabric and with small space heating requirements and overall low energy use. As a result of this the homes are thermally comfortable and economical to run and often can subsist from internal and external solar gains that are constantly being re-used – this is referred to as a Mechanical Ventilation with Heat Recovery (MVHR) Unit. 

The implementation of passive house standards can be at times strict and complicated, especially because there are certain guidelines and levels of targets that have to be met in order to obtain certification and recognition on the new building or in this case the retrofit.

More information on the processes used and in particular criterion that should be contemplated when planning to build and restore a building using the passive house system, can be seen by downloading the full case study using the link on the right. 

Performance

This investigation assisted with the development of a guide to evaluate the elements which can be considered, with some alternative approaches to achieving the Passive House criteria for a dwelling of this type.

This was especially developed for the fabric interventions on the building. The report will be a guide into what elements and constrains the building may present when looking into a more detailed design and construction method.

Alternatives for improving building fabric

The fabric intervention alternatives have given some scope of what is needed to be achieved in order to obtain lower heating demands and regulated thermal losses. It is important to focus on the airtightness of all elements, junctions and service apertures.

It is of extreme importance to have a carefully stripped internal finishes and core of the building in order to point out any possible decay or damage imposed on the building because of the passage of time and the lack of maintenance.

This will be a worthwhile investment in time and money as it will ensure that all subsequent work is done from a sound starting point. As well as airtightness, thermal bridging has a very pronounced effect on energy loss for well insulated buildings. If these bridges are not addressed they can undermine the performance of the building significantly and even lead to defects such as mould problems.

In summary, there have been some alternatives that are worth considering when designing further and investing into the passive house systems.

 

Calculated baseline and potential improvements in building fabric performance

More detailed information is available in the downloadable report to the right of this page.

Element description

Current state

U value (W/m2K)

Improved alternative

U value (W/m2K)

Front Wall

1.1

0.15/0.14

Wall right hand side, ground floor

1.1

0.15/0.14

Wall right hand side, first floor

1.6

0.15/0.14

Wall in bedrooms left hand side, ground and first floor

1.1

0.15/0.14

Curved wall in staircase

1.1

0.45

Party walls

1.6

0.4

Dormer Cheek

1.70

0.4

Floor

-

-

Roof

1.80

0.11

Windows

2.15

0.75

Doors

3.00

0.70

 

 

 

 

 

 

 

 

 

 

 

 

 

Lessons

Debate over the necessity into investing on “certified” Passive House products and achieving all the criteria as required by the institute poses the question of whether the passive house standard is cost worthy and worth the investment. It also poses the question whether applying this standard into the retrofit of older properties and hard to treat dwellings is technically viable and worth applying to the passive house criteria. It is evident that dealing with heat loss through the fabric is a concern and something that should be addressed, but should this be achieved using this standard or should it be achieved using similar criteria with a more environmental, conservational and cost effective manner rather than investing into over disciplined methods that may pose an enormous task in hard to treat buildings.

A more sustainable and holistic approach is preferred, that can take into consideration all fabric interventions as best as possible in conjunction with efficient heating systems as passive as possible with the use of an ecological conscientious approach with low carbon methods, low embodied energy of materials and healthy environmental alternatives that can create a building that blends in with the context and also with its surrounding environment. 

One of the main lessons learned is that a high level of skill is required, along with an understanding of the construction of the building to ensure that no damage is caused to the structure or to historic fabric and fixtures.

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