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Ventilation, heating and cooling in modern homes.

We have been heating engineers for many years and have always taken a great deal of pride in what we do. Sadly we have seen the level of expertise, knowledge and service drop mainly I believe to the market forcing skilled people having to work to low budgets brought about I believe by design professionals whose main concern is the bottom line and profit and lack of understanding of the project requirements.

Ventilation and cooling in modern homes

MVHR, Renewable energy Posted on Mon, August 19, 2019 12:52PM

Modern built homes are getting more energy efficient due to the use of insulation and breathable membranes houses are know being tested for air permeability. This drive to energy efficiency creates a major problem in that in the summer months even in the UK the buildings overheat which naturally is not conducive to a pleasant environment particularly during the night when we need sleep.

Good ventilation is a requirement and is easily achieved using a mechanical ventilation system but this though extremely efficient at filtering and removing the used air will not cool the house due to it being determined by the incoming temperature of the outside air temperature. In the summer months this temperature particular at night can be unbearable so what can we do to try and keep the temperatures to a reasonable level and condition the air.

Electrically driven air conditioning units are a option but they come with some major disadvantages, firstly they are expensive to operate and this overuse of electric is compounding the global warming issue and they need maintaining. Secondly they do not remove the used air but instead just recirculate it so any contaminants are not removed from the building.

The best option is to take advantage of what the earth provides for us for free and in this case it is through the use of passive cooling via the utilisation of earth pipes referred to as Ground Air heat exchangers so how do they work?

In the UK we are blessed with lots of rain and average temperatures which means that the grounds temperature 1.5 to 2 metres below ground remains at a fairly constant temperature of 7 – 12°C so the solution is to draw the fresh air to supply the ventilation unit through the earth and deliver the supplied air into the building within this temperature range and thereby cooling the incoming fresh air by as much as 13°C approximately depending on ground conditions in the summer with the added benefit of warming the incoming air in the wintertime by 10°C.

It is important to not here that the ground conditions play a major role in the effectiveness of this system the ideal being damp soil surrounding the ground pipes will perform rather better than free draining soil. Design considerations are important when using this type of system to achieve the maximum benefit for achieving these changes in temperature. The ground pipes need to be sized accordingly but generally speaking for a large property 60 metres of ground pipe with a diameter of 200mm would be required, this can be laid out in a pattern to optimise the soil conditions, Rehau make a excellent system.

Another design consideration when using ground to air heat exchangers is using the right pipe for this purpose, antimicrobial polypropylene helps protect again bacteria and microorganisms equally the ground pipe system needs to have significant fall to prevent standing water and this needs to be drained away via a condensate trap.

Another added option to further enhance the cooling effects in the summer months would be to include a cooling unit such as the Comfocool manufactured by Zehnder, this unit is designed to work with ComfoAir Q 600 heat recovery ventilation unit. The comfocool sits on top and provides a further 1.5 Kw of additional cooling if further enhancements are required.



Why doesn’t everyone use a heat pump?

Heat Pumps, Renewable energy Posted on Thu, January 29, 2015 04:43PM

So what has happened to heat pumps in this country? When I decided to give up my gas qualification and install heat pumps I genuinely assumed that heat pumps would be the future and demand would provide me with a good income installing them. I was wrong.

8 years later I have only installed a handful of ground source and air source heat pumps and the last one being 3 years ago, I think the reasons for heat pumps not being mainstream are many but it still surprises me when you look abroad to Germany and see that 85 per cent of new build has a heat pump in one form or another.

We work on high end very expensive properties where the clients will think nothing of spending huge amounts on their kitchens, communications and bathrooms fitments yet when it comes to the plumbing, heating and ventilation this is given little concern and generally treated by most Architects with disdain. I believe the reason the clients are not considering this aspect of the build design is poor information provided to them by the design professionals they have paid handsomely and is treated like an after though. The times I have been to site and seen the most appalling of installs with no care or design consideration given.

OK the long term gains are going to be good say in 10 years time, but how many people think that far ahead and more likely they will have moved house more than once in that time anyway. The big stumbling block in all this is simple – electricity – and why it costs 3 times as much as Gas after all even the worst heat pump installation will be more energy efficient than a fossil fuel gas boiler polluting the atmosphere.

Only when the government gets of it’s ‘arse ‘ and starts to develop electric generation on a large scale effectively and bring the cost of it in line with gas prices will i have any hope of making a living form installing heat pumps.



Best performing heat pumps, are they worth it and which one is best?

Heat Pumps Posted on Fri, March 29, 2013 12:25PM

This articles intention hopefully, is to help clarify the
reader as to whether a heat pump is worth considering and which manufacturer to
choose. I have looked at some of the top brands of heat pumps and chosen Air to
water heat pumps over Ground source to analyse, naturally ground source heat
pumps are/should be far more energy efficient than Air source, but I won’t go
into that here.

When you are trying to compare like-for-like between the
manufacturers as I have found it can be confusing as they may and do use
different parameters to demonstrate their efficiency, after all the only reason
you are thinking of buying a heat pump is will it save you money? So, in
looking at the different makes I kept it simple as you should and I used A2w35 as
my benchmark which indicates its COP (coefficient of performance) when it was
producing 35°C MWT (mean water temperature) with the outside air temperature at
2°C. Naturally when the air temperature is higher or lower the COP will be
different such as if the air temperature was 7°C then the COP will be better.

Unfortunately I am not going to name the manufacturers as I
can’t afford a lawsuit but it is easy enough for you to look up these
performance figures for yourself or you can always contact me directly for an
impartial view as an installer – www.subheat.co.uk
. Other than the actual performance more of which later, what other factors
need considering when choosing a heat pump? My view is it comes down to simply build
quality of the product and the reputation and service you would expect from the
manufacturers against the cost, when you are considering the purchase of such
an expensive item.

The cost of heat pumps is the biggest barrier against going
for this technology for most people unfortunately in comparison to conventional
heating boilers, the cost we were hoping was to be made more palatable with the
RHI (renewable heating incentive) but this looks not likely until sometime in
2014, so why should I buy one? I believe it come’s down to two reasons the
first is its a ‘clean’ technology energy source being electrically driven and
secondly and the major point is that it should be energy efficient and
therefore reduce your fuel bills.

So back to A7w35 and my findings for this I have looked several
heat pumps both ‘conventional’ and inverter driven around the 7Kw output range,
the three key point to consider are heat output, power input and the COP it
delivers at those temperatures – my conclusion to this is you pay for what you
get, quality will always outweigh cost in the long run – as a case in point as I
write this, I have received another phone call from a unhappy customer who had
a ‘well known’ heat pump installed by his builder/plumber and it’s not doing
what it is supposed to and would like for us to produce a report to confront his
builder/insurance company.

This gives us all a bad name in the heat pump business,
making heat pumps look as if they are not worth it when the truth is the exact
opposite but only if you get the right product in the first place from
installers who have the knowledge and design experience to give you helpful
impartial advice to carry the installation and only if it is appropriate for
your property. In conclusion do as much research and fact finding and talk to
people who know and don’t rely on people who don’t!



Ground source heat pumps design

Heat Pumps Posted on Fri, March 29, 2013 12:24PM

Article coming very soon



Ground Source heat pumps costs

Heat Pumps Posted on Fri, March 29, 2013 12:23PM

Article coming very soon



How does a heat pump Work?

Heat Pumps Posted on Wed, March 27, 2013 12:41PM

The Heat pump principle.

The refrigerant in the heat pump evaporates (Boyle’s Law) at low temperatures, the source energy whether air or water routes through the evaporator (heat ex-changer) where the refrigerant circulates. The refrigerant extracts the energy and the refrigerant changes from a liquid into a gas, a scroll compressor draws the refrigeration in and compresses it.

The increase in pressure raises the temperature. The compressor is is of a suction gas cooled designed so the energy/heat of the electric motor is not lost but reaches the downstream condenser together with the compressed refrigeration.

The refrigerant releases it’s absorbed energy to the circulating system via the condenser to the circulating system to the hot water and heating circuit, The expansion valve deduces the pressure of the refrigerant for the process to start all over again.