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Application for the variation of a planning condition. Ref. decision notice 16/00780/B
Condition 3 of our approval, for which we are seeking a variation, reads as follows:
"For the avoidance of doubt, all those windows shown with a transom (which is 21 no. in total) on Drawing number 18 (date-stamped as having been received 7th July 2016) shall be vertical sliding sashes and retained as such thereafter.
Reason: In the interest of the character and appearance of the dwelling hereby approved."
We did not initially have any concerns with the above condition from a purely aesthetic point of view and understand that the appearance of the windows is important to the intended traditional character of some parts of the building. However, the subsequent detailed design process has highlighted the issue that sliding sash windows are not available to a standard of airtightness that will allow us to employ a modern heat recovery system. This is an essential pre-requisite for the low carbon heating and ventilation system for which the house has been designed.
In our original planning submission, we emphasised our intention to build the property to a very high environmental standard and whilst the planning drawings do not show this in detail, the building control drawings, attached, demonstrate how we have committed to significant investment to achieve a very high standard of both insulation and airtightness.
An additional challenge that is faced is the very exposed coastal location on the northern side of Bay Ny Carrickey facing into the prevailing winds (South West) with no shelter or wind break. We understand that air and water tightness of windows has been a challenge for some of our neighbors and our research suggests that sliding sash windows would provide additional difficulties.
Considerable effort has gone into the design of the glazed elements of the building with a number of internationally renowned suppliers asked to provide products they are prepared to guarantee in a very exposed costal location like ours. The outcome of this research has been to specify triple glazing throughout the building for all windows and doors, with a thermal coefficient (u) target of 0.9 or below, and passive house standards of air tightness. We also require a salt resistant powder coating for the external aluminum frames. It has proved impossible to find a supplier who can meet the specification with a sliding sash design.
Our application has considered planning guidelines both relating to the appearance of dwellings in the countryside and more recent policy relating to sustainable development.
Planning circular 3/91, 'Guide to the design of residential development in the countryside' states that for building in the countryside 'the fenestration of vernacular dwellings is typically symmetrical with three upper front windows over a central doorway which is flanked by single windows. The upper windows may be smaller than those on the ground floor in some instances.
The windows are normally timber double hung sashes in comparatively small openings relative to a dominant area of solid wall surface.'
Our design is very much in line with these guidelines in terms of the arrangement, size, and appearance of the windows. However, we are applying to vary from the strict requirement for a sliding sash opening mechanism. This is based on considerable research into local environmental conditions, low energy building design and the approach taken to the surrounding buildings with similar aspects along that stretch of coastline.
As already noted the Development is sited in a very exposed position on Pooilvaaish road on the northern side of Bay Ny Carrickey. The property is approximately 11 m above sea level and the ground slopes away smoothly to the shore about 120 m in front of the SW elevation. There is no shelter from winds in a wide arc from due West to South South East.
The dominant front elevation of the dwelling faces due South West with no shelter from the prevailing winds. This has required all glazed elements to be specified to a high standard of both wind resistance and corrosion / environmental protection. We have only found one supplier, Velfac, (www.velfac.co.uk) prepared to guarantee the performance of their glazing systems to our requirements for insulation and airtightness on this site. We have also investigated alternative suppliers for the 21 traditional style windows relevant to this condition but all would recommend a casement style option with a traditional look if possible.
As well as considering the recommendations of the now 25 year old planning circular (3/91) referenced above, we have also taken into consideration the following from The Island Development Plan 'THE ISLE OF MAN STRATEGIC PLAN 2016. Towards a Sustainable Island' 'Strategic objective (b) To contribute towards reducing energy consumption by encouraging more efficient use of energy through conservation, recycling, and waste reduction. 4.3.8 The design of new development can make a positive contribution to the character and appearance of the Island. Recent development has often been criticised for its similarity to developments across the Island and elsewhere - "anywhere" architecture. At the same time some criticise current practice to retain traditional or vernacular designs. As is often the case the truth lies somewhere between the two extremes. All too often proposals for new developments have not taken into account a proper analysis of their context in terms of siting, layout, scale, materials and other factors. At the same time a slavish following of past design idioms, evolved for earlier lifestyles can produce buildings which do not reflect twenty first century lifestyles including accessibility and energy conservation.'
In this context there is absolutely no doubt that the use of a sliding sash mechanism as opposed to a more modern casement window design is a compromise to the environmental performance of the building particularly with regard to the level of airtightness which can be achieved (and sustained with normal wear and tear). This is a critical concern for us as we are designing the property to a standard which will allow us to do without a conventional boiler. This in turn represents a very significant reduction to the long term carbon emissions the property will generate.
In order to remove the need for a boiler we have designed for maximum airtightness and will be installing a modern Mechanical Heat Recovery and Ventilation System which relies on an airtight building design to function efficiently. The following advice has been received from our equipment supplier, SNX a respected company with local expertise. 'The proposed heating and ventilation system requires the lowest possible air leakage from the building to ensure the maximum energy efficiencies from the system. The MVHR system (Mechanical Ventilation and Heat Recovery) will only work sufficiently with an air tightness level below 3, which is $40 \%$ lower than the current building regulation requirements of 5 . To achieve this you will need to install windows and doors which are as air tight as possible. If the client is wanting to install opening windows the best option we have found from our experiences are casement windows. Ideally you would install as few opening windows as possible, you will not require any night vents in the window's as the fresh air will be provided by the MVHR system at a constant supply speed.
The heating and DHW will be supplied from a Tisun Proclean Thermal Store. The energy sources for this will be a high efficiency Heat Pump and a solar thermal system which will all be connected to the Thermal Store. To ensure the lowest possible amounts of energy are used by the heating equipment the property needs to be as air tight as possible to reduce the number of heat exchanges in the building per hour.
We have been the most active air tightness testing company on the Island for the last 10 years and in our experience we have not yet tested a building with sliding sash windows which has achieved a score under 3. Therefore I would suggest avoiding sliding sash windows when trying to achieve an air tightness below 3 to ensure that the energy saving measures being undertaken are the best they can possibly be.'
In support of this conclusion we have also consulted extensively with both on and off island window suppliers and with building control. Some examples are as follows.
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In considering our approach, we have looked at the surrounding building stock for approximately one kilometer either side of our site. Appendix 1 provides a comprehensive list with photographs and a location map. This research demonstrates that there is no precedent for retaining or installing sliding sash mechanisms in any of the properties in the local area. We were unable to find a single sliding sash window in any property and also found that the variety of styles and designs was such that the idea of a local vernacular is unsustainable.
The two closest properties are Spindrift and Sheerghlass. Sheerghlass is a new build on the site of an older dwelling and has casement windows of a similar design to those we are proposing. Spindrift is essentially a new build incorporating some elements of a much smaller previous dwelling with a wide variety of casement window styles on different elements of the building.
The condition specifically refers to the character and appearance of the dwelling. With this in mind we have been working with our suppliers to ensure that the casement windows they can supply (and guarantee) will retain the closest possible appearance to a traditional sliding sash design. Appendix 2 shows the drawings as currently approved and a new version showing the proposed windows which have been specifically designed with a heavy transom and which we believe are entirely in keeping with the character and appearance of the dwelling.
In working with our supplier (Velfac) they have suggested making a small sacrifice in the thermal efficiency of the windows to achieve the traditional appearance, as the thick transom element has a lower insulation value than the standard casement window. However, this does not compromise the airtightness and we believe it to be a reasonable compromise.
In Appendix 1. we have also included a photo of the cottage which was previously on this site. This did not have traditionally sized windows and they were not of a sliding sash design. Our design, regardless of the opening mechanism is much closer to the traditional layout as described in planning circular 3/91. This fact was specifically noted by the planning committee when our application was approved.
It should also be noted that the dwelling is set more than 100 m back from Pooilvaaish road and at that distance any differences in the operating method would be very difficult to discern. We feel that this is a very important point in that the $3 / 91$ planning circular only suggests that windows would normally have a sliding sash mechanism and whilst we are making every effort to preserve the desired appearance and layout, there is nothing normal about the environmental demands of the site.
In addition to the existing policy documents already referenced we also believe that it is important to consider the objectives of the current government as laid out in GD No: 20170002
OUR ISLAND: A SPECIAL PLACE TO LIVE AND WORK PROGRAMME FOR GOVERNMENT 2016-2021
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This document clearly sets out the Council of Ministers program for government for the next 5 years and explicitly states that departmental delivery plans will be based on the 20 outcomes and associated policy directives it identifies.
The following policy statements are clearly relevant to our plans and we believe that we are acting in accordance with the stated direction of government policy.
Enterprise and opportunity Island
'Support the three goals of energy security, the 2050 Emissions Reduction target and affordability to ensure an effective, secure and appropriate long term energy plan'
Responsible Island 'Deliver against our commitment to reduce our carbon emissions' Sustainable Island 'Consider innovative approaches to supporting people to make their homes and businesses more energy efficient.'
This final point in particular is difficult to ignore. We are making a significant (6 figure) investment in the energy performance of our new home by applying a combination of innovative technologies designed to massively increase the energy efficiency of the project. The insistence on sliding sash mechanisms for some of our windows seriously compromises this objective to the point where it would not be realistic to go for a boiler free design on this site.
In undertaking this the only support we are looking for is a rational evaluation of the arguments in the light of the aspiration to achieve a significantly more sustainable home in line with national (and international) best practice.
6. Summary.
We submit that the proposed change will be of little if any detriment to the character and appearance of the dwelling and that we have gone to considerable lengths to ensure that the design of the 21 windows that are the subject of this condition remains in keeping with the objectives of planning circular 3/91 in relation to dwellings in the countryside.
The proposed change will however be of significant benefit to the environmental performance of the building which is a key design goal and represents a significant investment in the quality of the Islands housing stock in line with the more recent objectives of sustainable development articulated in the Isle of Man Strategic plan and Programme for Government as quoted above.
If we further consider that the nearest publically accessible viewpoint is more than 100m from the proposed dwelling and that there has not been any precedent for requiring or retaining sliding sash windows in surrounding properties we believe that the environmental and functional benefits of our proposed traditionally styled windows far outweigh 'a slavish following of past design idioms, evolved for earlier lifestyles which can produce buildings which do not reflect twenty first century lifestyles including accessibility and energy conservation'.
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