Colorcoat® Column:Integration of rooflights with pre-finished steel cladding systems

In-plane rooflights can easily be included into profiled pre-finished steel roof systems requiring no modifications to the secondary steelwork and can supply light deep into large single storey buildings. Natural lighting, as well as providing benefits to the building occupants, can reduce energy costs and CO2 emissions, provided a balanced approach is taken to solar gain, heat losses and lighting levels.

What factors do I have to consider when installing rooflights?

The building designer needs to consider each building individualy as the operating conditions and building construction can greatly affect the requirements.

Rooflights can provide very significant savings in artificial lighting and associated CO2 emissions but only if they are installed in conjunction with an efficient automatic control for the electric lighting and cleaned on a regular basis.

The U-value of rooflights is significantly worse than the surrounding insulated cladding and more heat can be lost through the rooflights than through the entire insulated roof cladding. This has to be balanced against useful solar gains and reduced artificial lighting requirements.
Higher performing rooflights are available which can significantly reduce heat losses, however these are more expensive and this needs to be balanced against saving from other building envelope or service enhancements.

24 hour operations and introduction of high bay racking, within a building will greatly reduce the effectiveness of rooflights and increase use of artificial lighting.

How do I take these factors into account when modelling the building?

The introduction of rooflights can have a very significant effect on the CO2 emissions of a building, both in terms of compliance with Part L and actual building operations.

SBEM using the national calculation methodology (NCM) is a Part L “compliance modelling tool” and should not be used for “design modelling”. It calculates the CO2 emissions for an empty building using defined operating parameters. These parameters may be very different from those under which the building will actually operate and the results may therefore be quite different from operational performance. The NCM does allow direct comparison of the performance of similar buildings and this can be used to calculate energy performance certificate ratings for the buildings.

Where hours of operation and operating conditions are significantly different from those defined in the NCM and where high bay racking is likely to be installed, it may be beneficial to carry out specific design modelling to optimise lighting parameters for the actual building operations.

Even when specific “design modelling” has been undertaken it is a requirement of Approved Document L to meet the criterion for CO2 emissions which must be done by compliance modelling using the NCM.

Visit the Colorcoat® Technical Papers section on colorcoat-online for papers on Part L Compliance and Rooflights.

SolarWall® In Action Event – Comment by Stephen Fisher, Corus Colors

Stephen Fisher, Market Development Manager at Corus Colors, gives his take on the recent SolarWall in Action Event at the British Motor Heritage Museum….

Free heating, reduced fuel bills, reduced CO2 emissions, improved BREEAM ratings, excellent ventilation properties. Music to the ears of any building owner. Acting as a third skin to the building fabric, SolarWall® is a perforated Transpired Solar Collector which harnesses solar radiation to heat ambient air via a perforated collector.

Solar heated air is drawn from the external surface of the collector, through the perforations, before being distributed into the building where it is used directly as building ventilation or as a pre-heater for the building’s main heating system- reducing the amount of energy required to heat the building and associated CO2 emissions. New build and retro-fit buildings can utilise the technology which uses Corus Colorcoat Prisma® pre-finished steel. The level of initial interest for the SolarWall® product has been high.

Every time I have presented the offering alongside the Colorcoat® branded product offering, I have been met with requests for more information from the customer, or further meetings, to enable their other team members to hear about the benefits the CA Group product can bring to a project. So it was no real surprise to me that at the Motor Heritage Museum at Gaydon, venue for the SolarWall® in Action day this month, attendance figures were 40% over capacity. Representatives from a number of high profile clients, some of Europe’s biggest main contractors, along with developers and construction consultants were in attendance.

Some had heard of SolarWall® in part, others were new to the concept. The networking over with, the main presentations got underway. Peter Strikwerda, MD of Corus Colors, welcomed the audience and opened the proceedings with an insight into how both Corus and CA group were approaching the sustainability agenda. Kevin Bygate, Director of Product Development for Corus Colors, then set the scene as to why Corus and CA Group were so well aligned and had teamed up to help bring this particularly innovative venture to the market. The over-riding reason being a common understanding for the need for better performing buildings for future generations. Then it was the turn of Brian Watson, Commercial Director for CA Group, who took the audience through how SolarWall® works and the numerous benefits it can bring to a building. What struck me here was the amount of independent third party evidence which backed up the claims being made by the speaker. Reports by BSRIA, Battle McCarthy and the Swavesey report emphasised the benefits which SolarWall® delivers in terms of both energy savings and renewables (costs, percentage achieved etc.) The case studies presented at the end of the presentation also successfully demonstrated this. As I looked around the room I was greeted by the sight of an audience captivated by what they were hearing, the vast majority leaning forwards in concentration.

After presentations by Jaguar Land Rover, who are using SolarWall® on the nearby JLR Academy, and a short Q and A session, the audience were afforded the opportunity to see the system first hand and witness the energy savings it has bought to date, live, through monitoring equipment installed at JLR. The proof is in the pudding as they say. Listening to feedback on the way to the Academy, the information delivered so far had obviously been well received, comments such as ‘I’m seriously impressed with the payback time’ and ‘I will be looking to put it forward as a generic spec for my future buildings…’ was a testament to that. The tour itself only served to confirm what people had heard about SolarWall® earlier. The improved air quality in the building itself was a comment I heard several times throughout the visit. This coupled with evidence of the energy savings for the building seemed enough to have many people seriously thinking about the bonuses a system such as SolarWall® could provide to their building stock.

All in all the day itself was a huge success with numerous follow up meetings being made with interested parties with a view to lock SolarWall® into a number of project specifications. And with so many positives it is hard to argue against the offering.

Colorcoat® Column – perforated Transpired Solar Collectors (pTSC’s)

New renewable technologies are being developed for integration into the building envelope all of the time. The complexity of these technologies, makes the task of balancing cost against efficiency, one that is extremely difficult. Pre-finished steel perforated Transpired Solar Collectors (pTSC’s) offer a simple alternative renewable energy that can be used as a solution for new build or retro-fit.

What is a perforated Transpired Solar Collector (pTSC)?

The principle of the perforated Transpired Solar Collector is simple. Installed as an additional skin to a buildings southerly facing elevation, the system consists of a pre-finished steel sheet with thousands of tiny perforations uniformly spaced across the full face of the collector (termed SolarWall® ).

As solar radiation strikes the surface of the SolarWall® and is absorbed, solar heat conducts to the fine layer of air that lines the outer face of the panel (known as the thermal boundary layer). This heated boundary layer of air is then drawn through the perforations into an air cavity between the SolarWall and the original elevation behind. From here the fresh, heated air can then be fed directly into the building as heated ventilation air, or ducted into a heating unit to supplement the buildings heating system.

What type of cost savings can I achieve by installing a perforated Transpired Solar Collector?

Perforated Transpired Solar Collectors combine high efficiency with cost effectiveness. The savings it offers on heating bills means it can pay for itself in less than five years. Very few, if any, renewable energy solutions can get close to this short payback time. SolarWall® from CA group has a proven track record and can reduce heating bills by up to 50% and the total building CO2 emissions by up to 20%.

Does the colour of the pre-finished steel effect the efficiency of a perforated Transpired Solar Collector?

Black absorbs and white reflects light so naturally it is assumed that to collect solar radiation, the collector on the building’s external wall should be black – which may not necessarily complement the aesthetics of the building. Different colours have differing absorbtivity rates and this can impact on the efficiency of a perforated Transpired Solar Collector. It is important to ensure the most effective colour of pre-finished steel is specified whilst maintaining the aesthetic of the building. The colour range provided by Corus Colorcoat Prisma® is particularly effective for solar absorption and allows a wide range of colours to be used increasing the attractiveness of the building.

For more information regarding SolarWall®, visit the CA Group website.
For more information regarding Colorcoat Prisma®, visit colorcoat-online.com

Chatterley Valley wins LEAF Best Sustainable Development Award

Chatterley Valley, Stoke, which makes use of Colorcoat HPS200 Ultra® and Colorcoat Prisma®, has beaten off competion from all around the world to win the LEAF Best Sustainable Development Award, which took place on September 4th 2009 at the Ritz Carlton, Berlin.

Chetwoods Associates, the Architects behind Chatterley Valley, made use of the Repertoire® Colour Consultancy to create the striking graduated greens for the walls using Colorcoat Prisma. Additionally, with Colorcoat HPS200 Ultra in white on the roof, the combination of Corus Colorcoat Products helped the project achieve a BREEAM ‘Excellent’ rating, with the site itself including a variety of eco-friendly technologies which uses only 45% of the energy presently used by regulatory compliant buildings.

Other buildings short listed in this category included the Stadthaus E3 in Berlin, The European Investment Bank Building in Luxembourg and the Citi Data Centre in Frankfurt. Now in its sixth year, the LEAF Awards honours the architects designing the buildings and solutions that are setting the benchmark for the international architectural community.

The awards are open to all individuals and organisations that have made an outstanding contribution to the world of architecture. Previous winners have included the likes of Zaha Hadid, David Chipperfield, SOM, Steven Holl and Terry Farrell.

To find out more about Chatterley Valley, and to view the project gallery, click here.

Colorcoat® Column: Sustainable Refurbishment

There are many reasons to consider the refurbishment of an existing building. The need to refurbish will depend upon the condition of the building and its application. Quite often with industrial and warehouse premises the refurbishment is undertaken out of necessity e.g. for a leaking roof!

Refurbishment should be considered as more than extended maintenance. Instead it should be used as an opportunity to make significant changes and improvements to the building.

Refurbishment of an existing building can provide very significant improvements in thermal performance and reductions in operational CO2 emissions.

How does the embodied and operational CO2 of a refurbished building compare with a new building?

Examination of the embodied CO2 of a warehouse building shows that only 10%  is contained within the building envelope. Approximately 75% of the embodied CO2 is associated with the foundations and floor slab. Refurbishment of the building envelope, utilises the existing structure and will save ~ 90% of the embodied CO2 compared with a new build.

The refurbished building will be significantly more energy efficient and have reduced operational CO2 emissions approaching that of a new building and meeting the latest revision of the Building Regulations. The operational CO2 savings over the life of the building will be significantly greater than the additional embodied CO2 from refurbishing the building envelope. In many cases the refurbished building can have a lower overall CO2 footprint than a new building. The exact savings will be dependant on building type, size and application.

Which aspects of refurbishment will contribute most to reducing the operational CO2 emissions from the building?

Industrial buildings, constructed during the 1970s and early 80s have extremely poor thermal performance when compared with current regulatory requirements.

Typically they have minimal insulation with wall and roof U-values in the region of 2 W/m2/K. Air-tightness was not a specified requirement when these buildings were constructed and air-leakage rates in the region of 30 m3/h/m2 are typical. Current regulations require new buildings to have a minimum U-values of wall 0.35 W/m2/K and roof 0.25 W/m2/K and minimum air-tightness performance standard of 10 m3/h/m2. 

Refurbishment by either over cladding or a complete strip and re-sheet will show the greatest improvement in thermal performance and associated reduction in CO2 emissions.

Increased fabric insulation will generally show the greatest contribution as the initial U-values are so poor.Air-tightness will also show very significant benefits. For an over cladding refurbishment, a membrane must be installed underneath the additional insulation, otherwise there will be minimal improvements, as the external sheet will not provide an air-tight barrier.

With careful consideration, the operational CO2 emissions of a refurbished building can approach those of a new building and show reductions over the previous building of ~75% of the envelope related CO2 emissions.