Archive for the ‘Energy Efficiency’ Category

Solar Panels, the why and wherefore.

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The Organisation for Economic Co-operation and Development, the OECD, predicts that oil prices will remain stable over the next five years and may even come down by a small amount. There is nobody I know of brave enough or foolish enough to predict the same for electricity prices.

The British government recently signed a deal to pay the producers of electricity at the proposed Hinkley Point C nuclear power station twice the current price for their electricity when it starts producing in 2023.Twice the price at source does not necessarily mean twice the unit cost on your bill, currently about 17pence per kW/h in the north and 21cents in the south,  but with the amount of investment that will also be needed to update the existing supply network over the next 7 or 8 years, it might not be too far of the mark.

All of the above may well influence a choice of heating system in the short term but looking at energy matters in the longer term it’s not hard to conclude that oil and coal will, eventually, run out while it is an increase in renewables, (wind, wave and solar), combined with some nuclear that will keep the lights on. Solar panels may not immediately spring to mind as a possible source of energy in this country, given our climate, but there is enough sunshine, believe it or not, to make it worth considering in the medium term.

There are two different types of solar panels which, despite their grouping under the same nomenclature, perform in very different ways. Until recently the more common type to be found on a south facing roof was a water based system. These water based systems are, themselves, broken into two types, flat plate collectors and evacuated tubes. Water runs through the panels, is heated by the sun’s rays and is taken to your hot water cylinder where the heat is transferred to your hot water system for domestic use. Naturally the amount of heat you gain depends on the amount of sunshine hitting the panels and although there is some solar gain on a dull day, it is not significant. The systems require very little maintenance, I have had one on my roof for 23 years with only one service.

There was grant assistance for the cost of installing a water based system in southern Ireland up until 2011 through the Greener Homes scheme, unfortunately this scheme is now closed. Across the border in Northern Ireland there is no assistance at present, the industry is waiting for an announcement, due on 1st April 2015, under the Renewable Heat Incentive, which will determine the tariff owners of a system will receive as an annual payment. The cost of a system suitable for a three bed house, being 20 evacuated tubes, is approximately £2000.

The second and more topical system is a panel made up of photovoltaic cells. These cells generate electrical power by converting sunlight into direct current electricity using semiconducting materials. Although they have been around for about 50 years increases in manufacturing scale and sophistication have only recently brought them to a point where the return on the investment makes consideration worthwhile. A series on panels can be fitted either on the ground or on a roof facing generally south, but anywhere between east and west will do. The electricity generated can be used, once it has been changed from direct current to alternating current using an “inverter”, in a home or business or it can be “exported” back to the national grid.

In Great Britain and Northern Ireland there is a “feed-in tariff” for any electricity you generate from a renewable or low carbon source. This government assistance comes in the form of a ROC ( Renewable Obligation Certificate) payment of  16.32 pence per kW/h for every unit generated, regardless of what use you put the electricity to. These payments are restricted to 4kW systems for domestic installations and 12kW for commercial premises, (or 50kW if you have a 3 phase supply). If you generate more than you use in your home or business you can sell, or export, the excess back to the grid, although you will only receive around 5.1 pence per unit in return. A good quality system designed to generate 4kW will cost around £6,500 stg. If you take into consideration the annual ROC payment, usually around £550 depending on how close to direct south your roof faces and what shading there may be from trees or buildings, and add the saving you make to your electricity bills of between £300 and £500, depending on your use, you can achieve a payback of  around 6 years. It’s worth noting that your Roc payment will run for 20 years and, if the price of electricity were to double, the saving on your bill could increase to between £600 and £1000.

Sadly there are no ROC payments in Southern Ireland. Until recently you could sell excess electricity back to the grid and at a more generous rate of 9 cents per unit, but only from domestic systems.  In a recent announcement Electric Ireland stated that they will no longer buy electricity from residential properties generating electricity from renwable source such as wind and solar. In addition VAT on systems in the north is charged at 5% while those in the south are charged at 13.5%. As Ireland faces fines of “ hundreds of millions of euro per year if we don’t ensure that 40% of our electricity demand comes from renewable sources by 2020”, it’s hard to see why the Irish government is failing to encourage more domestic investment in this technology. Despite this, many Council buildings in the south are currently being fitted with PV systems designed to provide just enough electricity to meet their own needs. Considering a payback in the south of between 10 and 15 years, perhaps it’s only Councils that can find and justify the capital outlay. “The UK currently has about 3,400 megawatts of solar power installed, Germany plans to have 66,000 megawatts by 2020, Ireland has less than 1.”

“Lies, damned lies and statistics”, in that order, to quote Oscar Wilde.  It’s easy to put figures to possible future performances to prove a point and from the outside investing in a 4kW photovoltaic system in Northern Ireland under the current government deal does seem like a bit of a “no brainer” and that’s at the current price of electricity. Whether or not to invest £6,500 with a return of around £20,000 over 20 years with the bonus of a reduction in your vulnerability to the vagaries of energy prices might not need a lot of pondering and on that basis we now have “pv” panels on our roof. We will monitor the system’s performance, compare it with the predictions and report back but in the meantime, a note of caution on the timing.

A consultation paper was launched by the Department of Enterprise, Trade and Investment into possible changes to Northern Ireland Renewable Obligations (NIRO) and we understand that the paper recommends reducing the value of the ROCs payments by about 60%. DETI has received around 300 negative responses to such a proposal and we are led to believe that from April 1st 2015 a less dramatic cut of 40% may be announced. This would extend the payback time from approximately 6 years to 8 or 9 years. Anyone who registers their system before the announcement will get the current rate for the full 20 year period.Burns - Enniskillen PVI

Energy Watch 2 – Site Selection

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In the forthcoming articles for Energy Watch we will divide our comments into “New Build” and “Existing” but we hope that existing and prospective house owners will find time to read both sections as there are many ideas and philosophies that apply across the board. The big idea is that we do our bit for the world by reducing our carbon emissions (caused by burning fossil fuels), and the bonus is that in doing so we reduce the running costs of our homes. This week we are going to concentrate on site selection for a new build, as the obvious starting point.

Some people have the luxury, and indeed the excitement, of searching for the site for their new home, while many others obtain their sites from family lands. In this article we are going to concentrate on the two main elements of site selection that affect the future energy use of your house: its orientation and the shelter.

The orientation: where the sun rises and sets in relation to your site

In recent times, the way you face your house has usually depended on where the public road is. Most people place their house parallel to the road or facing where any views might be. As a result, the roof and windows usually face the road or the views, and the position of the sun is not so much taken into account. However, the amount of glass and the positioning of windows in your house are major factors in terms of your future heat loss and gain, so the position of the house in relation to the sun is vitally important. The roof is important as it is where solar panels and photovoltaic panels are most likely to be located, and they need to face the sun.

When sunlight comes through a window your building experiences solar gain i.e. you get heat from the sun. Just step into a green house on a sunny day for a quick demonstration.  The first rule in positioning windows is to put the absolute minimum amount of glazing on your north facing elevation where there is little solar gain, and put the maximum amount on your south facing elevation to take advantage of the sun’s heat and light.

For site selection the ideal site is one that has the access road on the north side, where you can put small windows to protect your privacy, and on the south side expansive views which you can make the most of with large windows to obtain maximum daylighting and solar gain.  If only life were that easy! It’s worth remembering that the windows are among the weakest points in your house as far as heat loss is concerned, so careful consideration is needed to balance the exploitation of views and solar gain against the heat losses that go with large windows that are inappropriately positioned.

It makes sense therefore to organise the house layout so that the main living accommodation is to the southern side of the house and the utility and service rooms are on the northern side. Following this logic, bedrooms might be on the east to catch the sunrise and dining/patio areas might be on the west for maximum appreciation of the sunset.


In years gone by houses were generally placed in more sheltered spots as there was an inherent understanding of the effects of weather on the use of a dwelling.  The front door rarely faced into the prevailing south-west wind and of course windows were small. This had the effect of reducing draughts caused by wind pressure, because the old houses were quite leaky in that regard. Nowadays, we try to make houses very airtight to avoid draughts (and thus reduce heat loss), but the old principles are still relevant and worth considering at an early stage, when you are deciding where to position your house on the site. In spite of our modern building technologies, it’s still better to avoid building on exposed sites.

On the vast majority of sites compromises have to be made and each site will Site selectionhave its own unique solution.  As an example we show above an existing site where we are constructing a passive house close to a lake.  As you will see the access road is on the east, the views are to the south and west and the shelter is provided to the northwest. Clearly this is not the perfect site so a) we took the access from the road around to the back of the house so that parked cars would not sit between the house and the view and b) we angled the windows to pick up the sun and the views.


Introduction to Energy Watch Articles

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What can we do to offset rising energy costs?

Other than hassling our political representatives it’s unlikely one can do much about the cost of petrol and diesel but there is a lot you can do to reduce the cost of running your home and you can do even more if you’re lucky enough to be building a new home.

Over the next few issues, are going to put a few ideas to you that we hope will help to reduce those energy bills.  A lot of what we set out will be just common sense but we will advise you of the latest technical solutions and point out some of the many pitfalls.

Clearly a new build is a great opportunity to reduce your future energy bills to a very low level and we will give advice on the many aspects that you should consider when starting to build, such as site selection, heating methods and life style changes. However, no matter how many new homes we build over the next decade or two, that number will be dwarfed by the number of existing houses, many of which have been built prior to the 1973 oil crisis with very little concern for energy usage.

As money is a main driver, we are leaving aside such minor matters as global warming, rising sea levels and the expansion of the deserts and we will relate all our advice to “value for money”.  Some solutions such as reducing the number and size of north facing windows on a new house or insulating your existing attic are not huge costs and have a relatively straightforward and short term payback, (the time taken to recover the money you spent on the work in the form of savings in your energy bills).  Others, such as triple glazing a new house or insulated external plaster to an existing house, take a bit more consideration.  We will let you know what grants are available on energy saving measures and, will also hope to throw in a little education.  What’s the difference between a “Passive House” and a “Zero Carbon” house?  What is “geo-thermal” and how does it work?

We would also invite any readers to send in questions they may have and we’ll do our best to answer them based on our experience.

Some of the topics we will be covering over the next articles are

  • the effects of lifestyle on your bills
  • insulation and cold bridging
  • ventilation and air tightness
  • rain water harvesting
  • grants
  • the Passive Haus
  • retrofitting
  • the integrated approach
  • your site
  • solar gain
  • low energy lighting
  • double and triple glazing
  • photovoltaic cells
  • solar panels
  • geo-thermal and air to water systems
  • wind turbines
  • heat recovery systems


If you have any other related questions or topics for discussion, contact us on our Facebook/Allan Curran Architects, or by emailing us on