Stuart Cooper, Managing Director of SOLFEX energy systems reports on the key points of the impending new standard for pitched roof installation kits – MCS 012
Since the feed in tariff was introduced in April 2010 and many years prior to this, hundreds of thousands of photovoltaic & solar thermal systems have been installed. Although all current modules and solar thermal collectors have their relevant MCS or Solar keymark certification, what about the substructure holding them? From the 31st March 2014 all this is about to change with the introduction of the new MCS 012 which will give the industry a clear set of standards to operate within.
The new standard & performance criteria will cover the following topics: • Resistance to wind uplift • Weather tightness • Fire • Installation Instructions
The requirements of this new standard are not applicable to installations on flat roofs which will be covered by a separate document.
One performance criteria of the new standard requires conclusive testing of the mounting system with installed modules or solar thermal collectors for the resistance to wind uplift, a maximum wind uplift resistance shall be declared according to BS EN 14437: 2004 (Determination of the uplift resistance of installed clay or concrete tiles for roofing – Roof system test method)
This testing method for resistance to wind uplift is exhaustive and simulates real world installations with the minimum specification for rafter spacing and batten fixing with actual roof coverings installed according to BS 5534: 2003.
Conclusive and successful testing will ensure that installers are being supplied with a quality mounting structure which is fit for purpose and designed for the life of the product. Over the years I have seen numerous examples of poorly installed solar thermal installation’s which use various metal strapping systems or bolts which are clearly not fit for purpose. These either cause damage to the roofing fabric which leads to water ingress or the fixing method isn’t secure. MCS 012 should hopefully halt these bad examples.
Two other performance criteria’s which are examined are weather tightness & resistance to fire for roof integrated thermal or photovoltaic products. The mounting of solar panels on or in the roof shall not decrease the weather performance of the declared roof types. A fire rating shall also be declared in accordance with MCS 012 for roof integrated products which satisfies BS 476-3 2004 or DD ENV 1187:2002 Test 4 and the rating must be declared.
The new standard also gives clear guidelines to installations using hanger bolts which have been a popular choice for installers over the years; however, not all of these installations have been ideal and have resulted in broken or cracked roofing tiles or slate leading to water ingress due to stress of the weight load of the solar thermal or module array directly on them.
MCS 012 states for new hanger bolt installations should meet the following requirements: • The bolt or flashing shall not transfer any load on the slates / tiles (excluding metal tiles or sheets) beneath. • The system shall not rely on site applied silicone, mastic or other similar type sealants as the sole method to provide a weather-tight seal. • The system must durably seal every layer of roof covering that is perforated by the bolt system. • The system shall not rely on a sealing washer or plate that presses down on the slate/tile (excluding metal tiles or sheets) to ensure a weather tight seal. • The bolt fixings shall not be fixed into the battens.
Mounting Installation instructions must list compatible solar panels and roof systems. This information must detail to the installer clearly how the system is installed including the type and number of fixings along with the maximum recommended spacing distance of these fixings. Installation instructions must also indicate which roof type coverings are compatible with the fixing system.
Other information which the installation manual will detail is the maximum wind load the system achieved when assessed according to the MCS 012 standard, using the standard procedure and fixing details as described in the manufacturer’s instructions; For products that can be used with a variety of different solar panels these instructions should clearly describe the array design constraints (e.g. maximum module area, fixings per m² etc) that need to be met in order to achieve the stated wind load result.
Products complying with the standard will be clearly labelled with the Approved Product MCS label along with a certified registration number. All SOLFEX energy systems solar thermal & photovoltaic pitched roof mountings kits will be fully certified when MCS 012 becomes mandatory on the 31st March 2014.