Construction Phase

The construction phase of the project involved integrating the dynamic roof into the standard CALA construction method. Energyflo™ cells were initially placed into trays.

Vist the gallery to see more imagesTrays with instrumented cells were assembled and tested with assistance from Engineering Workshop staff at the University of Aberdeen .  The other ( majority of) trays were delivered to site fully built from the manufacturer . Both sets of trays arrived at the same time to coincide with the construction of the roof.

The construction phase was completed by placing and fixing the trays of Energyflo™ cells into the roof structure at ground level. The process of fixing the cells gave valuable opportunity to allow site workers access to the technology and allowed the project team time to analyse the performance of the cell in terms of its fitting durability and ease of use.

img2Problems did occur in the placement of the system. This was due to the dimensions of the timber A-frames not being as expected. This had the cumulative effect of adding around 5mm per bay to the timber structure. While this could be accommodated over three or four bays it eventually became too great and some of the trays had to be modified on site . As this was a bespoke project it was possible to take the time and care required to do this and still place the system successfully.
This episode in the placement of the Energyflo™ cells was eye opening. All parties were aware of the requirement to adhere to specified tolerances. However a third party supplied the timber for the roof and provided thicker joists as there was not the requested size immediately available. This is standard practice to ensure the minimum of delays. The timber supplied provided a stronger roof but was not expected by any party and so adversely impacted on the time available for placement. Adjustment of the trays was possible but highlighted the risks that must be managed and conveyed to all partners and suppliers when using a new product. In standard construction the different timber widths would not have been noticed.

Roof placement

After the trays were fixed in place, by nailing overlapping sections, the roof was lifted in place. Two bays on either side of the roof were left open to allow the roof to be lifted in place, with the remaining 4 trays placed and nailed down in situ. This process brought some insight into the practices that occur whilst lifting a roof and in general the rough treatment that can occur on site. During this process some of the cells were damaged despite the efforts of the site staff to avoid this. A couple of hammers were dropped which cracked the outer surface of the material. In addition a crane hook also hit the cell surface. In all of these cases the damage was superficial but highlighted the risks involved in having a relatively fragile casing for the product, the expanded polystyrene shell, around construction tools and machinery.

Exposed energyflo™ cells

After the roof was lifted into place the weather visit gallery to see more imagesdeteriorated as can occur in October. For health and safety reasons the roofers were not able to commence work on weather proofing the roof. This left Energyflo™ cells exposed to high winds and rain for over a week which proved to be an interesting durability test for the product. Over this time there was no deterioration to the fabric or structure of the cells. As all the materials involved in the tray system were inert this was expected. There was some concern over the rain that lay in the trays as the bottoms was sealed and therefore could trap water. Whilst this did occur to some extend the trapped water evaporated from the trays quickly once the weather improved and the weather proofing was complete. Air was able to pass over the trays allowing drying even after the weather proofing was in place.

Roof perforations

Placement of vent pipes was another issue to occur on-site. In the project all the vent pipes were specified before the system was placed. With this in mind, blank (solid expanded polystyrene) cells were specified at these locations. The cells were then cut through rather clumsily on site leaving large holes for the pipes to go through. This section of the construction could have been handled slightly differently as the process of adding the openings for the pipes turned out to be rather messy. A fair amount of work was required to repair the damage and seal the system on two levels. After this experience it is now possible to address this issue for future projects with pre-prepared cells that can include vent holes or any other type of opening.

After this the trays had to be connected together and brought to the heat exchanger to allow it to be distributed to the rest of the house. This was a case of extending the ductwork in the attic. The is a relatively complicated feature of the design that was required to connect all the trays together. This was completed as per the design specification. A simpler system configuration for commercial application would reduce the design and installation cost.

The results of the construction phase were by-and-large qualitative.  In terms of construction and design know-how, though, it remains an extremely valuable phase of the project.

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Sponsors The University of Aberdeen EBP Cala Carbon Trust