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So, the U value of the window
in those locations is 3 or 3.2,
that sort of order.
Compared with if we were designing for example
to German PassivHaus standards today,
we would go for 0.8 – so, a huge difference.
The walls we had at 0.25,
again if it were to PassivHaus standards today
we would be going for 0.1 or thereby but that's
relatively easy to upgrade.
The combined effect of double glazing on the
outer skin of the buffer spaces and the inner
glazing actually gave us U values of below 1.2
at the average U value taking into account
both sets of glazing.
So, in fact, to get that down to 0.8 would
be a relatively simple matter.
The other weak link in the scheme of things was the way people,
having got a relatively inefficient heating system by today’s standards,
there was the question of how they set thermostats.
Now, that would still be an issue today regardless
of how efficient the boiler was.
What we found at Easthall was that people who set
the thermostat to a comfort level in the living room
and didn’t really make much use of radiators in the
other spaces were by far and away more efficient than
the people who set their thermostat high
on every radiator in the house.
Actually, the interesting thing is that if one
compared the lowest consumer with the highest consumer:
2 things - the temperature in the living room didn’t vary much at all,
the temperature in the rest of the house would vary significantly,
but not dramatically.
The comfort levels from the lowest consumers were still reasonable.
The other big difference was the rate of air change.
So, there was a large difference between the
lowest consumer and the highest consumer.
The lowest consumer was just below
25 kilowatt hours/m2/annum for space heating,
the highest consumer was 215 - an enormous difference,
a differential factor of 8.7.
So there we have it, the key thing was the issue
of how thermostats were set and how ventilation was regulated.
The final weak link was the air collectors itself.
So, this was one of the buffer spaces with clothes drying.
So, we see we have got moisture out of the buffer space.
This was the initial sketch working drawings showing the
upgrading to insulation in the roof and both buffer spaces on each side.
This was the schematic for the air collector.
The function of the air collector,
having got the space heating down to a lower level,
was actually to tackle two things.
One was to pre-heat the domestic hot water and the second was
to include the entrance stairwell into the circuit
and so that would be slightly pre-warmed.
So, the air collector took air from the top of the stairwell,
heated it up on a sunny day,
and that then went through an air to water heat exchanger,
heating the water, and then a fan took the,
if you like, the “loose change” from the thermal benefit
down to the bottom of the stairwell,
from where it’s circulated up to the top again.
The weak link was actually at the exchange.
Initially, the system was tested out with re-used radiators
from a transit van which was highly efficient.
Unfortunately,
it was found that that was in aluminuim and the risk
was it would start to react with copper piping,
and so those were replaced with purpose-made units
which were much less efficient.
However, the set-up, the collector itself worked well
and with an efficient air-to-water heat exchanger
it was proved to be perfectly viable.
So, we’ve pointed out all the weak link
factors of the Easthall project as it was.
Nevertheless, all sounds very negative,
but at the time it brought whole-house heating to a
considerable level of comfort within the scope of all the tenants,
even the ones that were heating to the highest level,
ventilating to the highest level and therefore spending the most money,
found it affordable.
But how do we get that down to zero-carbon and what
zero-carbon are we aiming for? Well,
the target was to see theoretically if one could take
a house today down to zero space-heating carbon emissions,
zero water-heating carbon emissions,
and also the other regulated uses such as
lighting and pumps to circulate the water and any fans
such as this fan here to circulate air.
So, in other words, the Scottish regulated energy uses,
can we get that down to zero-carbon?
Well, looking at the plan, the obvious things to tackle
first of all are upgrading the wall to a higher standard.
That’s relatively simple – all we need is more insulation on the outside.
To get the windows to a higher standard,
say a PassivHaus standard,
To get the buffer space combination down to 0.8 is less demanding.
We can then address also upgrading the insulation
in the party wall positioned here and other small
parts here with internal insulation.
That’s the easy bit.
The tricky bit is then addressing the
heating and ventilation system in an energy efficient manner.
Having got the U values down to that kind of level,
the peak surfaces 0.1, windows 0.8,
really we don’t need much of a heating system.
So, instead of having, as shown in the original plans,
radiators in all the rooms, the option that I’m looking
at as viable would be to have a
heat recovery unit located for all three flats up in the attic space,
recovering heat from the wet areas, and linked
to an air-source heat pump.
There are two possible locations for this.
One would be in what was originally a fuel store.
That means it’s accessible still off the common stairwell.
And, if both the heat recovery unit and the
air-source heat pump were located there,
one could then deliver warm air through the now redundant chimney.
In other words, instead of taking air up through the chimney and out,
air would be delivered through the roof space to the
top of the chimney head and then down,
delivering into bedrooms and the living room.
That then leaves the minor bedroom and the bathroom.
The bathroom would probably have a towel rail and
still a small radiator possibly in the smaller bedroom.
The kitchen wouldn’t need any heating at all because
it’s got plenty of incidental gains from the equipment.
So, a very simple system with a very small load would then be feasible -
this combination of a heat recovery unit and an air-sourced heat pump.
That, then, would be the key proposal in terms of then meeting those loads renewably.
So, of course, one then looks at how we would do that,
and clearly we’ve got a roofscape.
At the moment, there’s 10 m2 of air collector
which is addressing hot water on that roof.
If that was retained in a new 2010 upgrade,
it would leave something like 45 m2 of roof surface in addition to the 10 m2,
which could be solar photovoltaics on one side.
Now, of course, the possibility exists
- we’ve got glazed spaces on each side of the building,
orientations change.
We could actually make use,
depending on orientation,
of more than one side.
And, if we just stick to the idea of using one roof surface,
that would give us 45 m2of PV,
in other words 15 m2 for each of the
apartments on each side of the stairway.
And, that should yield enough energy to cope
with the small space heating load of roughly,
I would estimate,
800 kilowatt hours for the space heating and enough
left over to meet lighting and pumps and fans.
So, it’s within the grasp of an upgrade.
Of course, the issue might well be cost,
but we’re now entering a new phase of feed-in tariff
and therefore the economics of such a roof
with both solar-thermal and solar-electric,
solar photovoltaic, would make that feasible.
The whole thing, of course,
is predicated on a fairly significant financial upgrade,
but one must bear in mind that provided,
one assumes, that 3-storey tenement flats is a viable housing form,
and I would suggest that given the evidence from
right-to-buy on such accommodation it still is a viable form,
and provided that the capital investment is
there to bring new values to that value,
the PassivHaus value essentially,
that the whole thing is a reasonable proposition.
Of course, this is a particular case study.
Nevertheless, that type of approach could be used
for other low-rise housing of this form.
Other problems exist for high-rise but I’ll
leave that for my colleague to discuss.
Thank you