St Mary Redcliffe Project 450 RIBA 2 Stage End Report

1563.R1 – Stage 2 report Page 15 of 29
This would also provide heat for hot water production. This option has been discounted due to foreseen issue in
coordinating high level flues to discharge the products of combustion.
Air Source Heat Pumps – Air to Water – External packaged condenser plant produces LTHW all year around. Dedicated
pumping plant complete with pressurization and ancillaries requires an internal plant room or GRP enclosure adjacent
to the external plant space.
This option is most efficient at relatively low water temperatures and is therefore suited to slow reacting heating
strategies such as under floor heating making use of high thermal masses. Radiators can be included, but need to be
oversized to accommodate the lower distribution temperatures.
It is possible to extend this option to generate hot water to serve the kitchen, however,
based on the size and likely usage of the kitchen, this option will likely be inefficient.
Heat Emitter Options
Option 1: Heating to the new build areas can be provided via an
underfloor heating system.
Special plastic pipework would be buried into the floor and piped
back to manifolds. The components of the underfloor systems
are all hidden from view.
Underfloor heating systems have a much longer ‘lag’ than
traditional radiators i.e. they take longer to heat up a room and
longer to respond to changes in the system temperature settings,
but they are generally ‘invisible’.
This is the preferred option for the heating plant serving the North side of the new
development.
Air Source Heat Pumps – VRF – As above, external condenser units are required, but in
this instance, refrigerant is distributed to internal Fan Coil Units (FCU). Heating and
cooling can be provided with this system. As cooling is anticipated to be required to the
events space, this option is considered for these areas.
District Heating Connection – Bristol is currently extending a district heating network in
close proximity to St Mary Redcliffe Church. Plate heat exchangers and associated
pressurization, pumps and controls will be required.
Due to uncertainty with regard to the construction programme of the district heating
network, this option is not feasible for the development. It will, however, be considered
for future connection. The proposed Air Source Heat Pump plant could be disconnected
and replaced with plate heat exchangers at the end of their economic life to make use
of the available district heating.
Packaged Air Handling Plant Providing Heating – Areas with high air volumes can be heated and cooled by heating the
fresh air supply. This is a potential solution for the events space and the Hogarth Gallery. As these spaces have fairly
high occupancy, this drives a high supply air volume requirement, which has the capacity to provide space heating.
A packaged AHU will use a refrigerant compression and expansion system to take heat from exhaust air and “reject” this
into the supply air stream. A thermal wheel will also be used to recover heat from the extracted air.
This option reduces the required external plant in instances where high air volumes are already required.
Underfloor heating systems work well with the low flow temperatures of VRF systems.
Option 2: Heating to existing refurbished areas can be provided via traditional steel panel radiators.
Radiators can rapidly heat-up a space and are individually controllable by the users. They work well with the high flow
temperatures produced by conventional boilers but require oversizing if used with low flow temperatures associated with
VRF systems.
A number of options are available based on the requirements of the architectural aesthetics and the necessity to protect
from scolding.
Cast-iron radiators (or limited ranges
available in steel) can be provided in
areas where the traditional ‘feel’ of
the building is looking to be
preserved. Radiator shapes and
locations can be agreed in
conjunction with the Architect to suit
the aesthetics of the rooms.
Alternatively, flat panel radiators, located under windows (where possible) or along
walls, can be located in less architecturally sensitive areas. As with the low-level
radiators, shapes and locations can be agreed in conjunction with the Architect to
suit the aesthetics of the rooms.