Moving up the ladder


Do you want to improve the energy efficiency of your home but don’t know where to start? With the help of careful planning, research and a good team of consultants, you will be well on the way to reduced energy bills and a healthier home.  

In the building trade, a ‘retrofit’ usually means an energy upgrade; it’s not to be confused with a refurbishment which is a cosmetic exercise. A carefully devised retrofit will reduce your energy bills and will add value to your property but as with any poorly carried out building works, a poorly thought out and poorly executed energy upgrade will have the opposite result !

A form of investment 
When investing your money it is typical to consider the advertised options available like bank savings, the stock market, oil futures or carbon emissions trading. It’s very unlikely you would consider investing in your home.

But as with any financial instrument, the best advice is to invest in something you understand.

ROI has almost two million dwellings, 52 percent of which are houses which were built prior to the introduction of the Building Regulations. Over half of the houses which have been assessed using the Dwelling Energy Assessment Procedure (DEAP) have achieved a D1 BER (Building Energy Rating) rating or lower.

NI has over 750,000 thousand dwellings, half the houses assessed using the Standard Assessment Procedure (SAP) achieved no more than a 59 or D on the Energy Performance Certificate (EPC) scale, which is very much in line with the ROI situation.

Not sure what DEAP or SAP is? They’re Ireland’s (ROI and NI respectively) official methods for calculating energy performance and carbon dioxide emissions as a result of heating water, central heating and lighting your home.

Rising energy prices will increase the running costs of these houses considerably in the coming years, which will decrease the attractiveness of these properties in the future thus reducing their value to potential buyers.

In addition your retrofit will create a healthy environment for you, the occupant, and for your surroundings by reducing the level of energy your building consumes, which results in a reduction in the level of pollutants released into the air.

To carry out an energy upgrade you must start by establishing what you have. The approach is to calculate your existing energy rating with a survey (baseline BER or EPC) carried out by a suitably qualified professional consultant.

The survey first looks at the existing fabric to identify the type of construction. This can

often be done quite easily; wall thickness and type of material s used can be established by unscrewing any ‘hole in the wall’ type ventilation panels and simply photographing the opening and measuring the thickness of the fabric. If wall vents are not present, measure the external wall thickness at door or window openings, this should give you a good indication of the form of construction.

The attic is then inspected to establish if insulation is present – type and thickness. Windows and doors, meanwhile, can quickly be identified as either single (one pane of glass) or double glazed.

The type of heating (or systems data) in your home is also inspected. Do you have gas or oil, with or without immersion? The boiler model, presence of insulation on heating pipes and lagging jacket on the hot water cylinder and type of heat emitters (radiators or underfloor heating) are all recorded.

In ROI the collated data is inputted into DEAP to establish your building’s baseline BER, while in NI this is inputted into SAP to establish your baseline EPC.

Once the baseline is established you can set your goal for the retrofit, so if the existing house has an F rating and you want to take it to an A2 or a C2, this survey will help you to establish this while setting your budget and specification for the works.

Solid and narrow cavity wall homes 
Now let’s take two house types commonly found across Ireland and describe some of the things that can be done to reduce energy costs and carbon dioxide emissions.

Firstly a solid wall type house, built between the 1930s and 1950s and secondly a narrow cavity wall house built between the 1960s and 1970s. Both are suitable candidates for a deep energy retrofit.

The solid wall type house typically has a 215mm thick mass concrete wall with an 18mm cement pebbledash plaster finish externally and an 18mm ‘wet’ gypsum plaster finish internally.

The narrow cavity wall house typically has an empty cavity of between 50-100mm with a 100mm brick or concrete block and render outer wall and 100mm inner concrete block wall.

Detailed below are typical issues with these house types**: 

  • Roof is pitched with no insulation resulting in a roof U-value of 3.91 W/sqmK.
  • Solid External walls with no insulation resulting in a  wall U-value of 2.47 W/sqmK.
  • Narrow Cavity Wall with an empty cavity of 50mm with no insulation resulting in a wall U-value of 1.66 W/sqmK.
  • Floors are solid concrete with no insulation resulting in a floor U-value of 0.61 W/sqmK.
  • Windows are double glazed air filled frames resulting in a window U-value of 3.1 W/sqmK.
  • External doors are solid timber resulting in a U-value of 3 W/sqmK.
  • The primary heating is a gas fired boiler with uninsulated pipe work with 65% * fuel efficiency.
  • The secondary heating system is an open fire with 30% * fuel efficiency.
  • Water heating is provided by the primary gas fired boiler with an electric immersion used during the summer.
  • The hot water cylinder has a loose fitting lagging jacket of 25mm thickness with no thermostat.
  • The only system control is a programmer.

All this data is collated and inputted into DEAP to establish a baseline BER for these examples. The solid wall house typically achieves an F Rating, while the narrow cavity house achieves a G Rating.

An alternative to solar water heating is to install 2kW of photovoltaic (PV) panels – solar electricity – along with an immersion dump. This will provide all the hot water and day time electricity that is required for a normal house. If you are installing a heat pump, then using night rate electricity for hot water may render this uneconomical.

In conclusion  
These examples achieve an 84% reduction in energy usage and an 85% reduction in CO2 emissions per year. A house with a BER rating of F typically has a primary energy use of 429kWh/sqm per year with annual fuel costs of €1,437 per annum (based on current fuel cost data***). While a house with a BER rating of A2 typically has a primary energy use of 44kWh/sqm per year with annual fuel costs of €98 per annum. A retrofit like this is clearly repaying the investment. Fortunately it’s also something you can do in stages.

The net result for you the occupier is that you have invested in the future of your home, reduced your energy bills and increased your home’s value while creating a healthy environment for all.

Finally, it is very important when considering retrofitting your home that you seek professional advice in advance from an architect or engineer with specialist retrofit skills.

Additional information 
Paul Kenny B.E. C. Eng. MIEI, CEO of the Tipperary Energy Agency, tel. 052 7443090,
* Efficiency levels are taken from the DEAP manual Table 4a. and the SEAI Harp database
** U-Values have been calculated using a dedicated professional software package, note retrofit U-value results will vary depending on specification of materials
*** SEAI Energy Data Portal

Proposed fabric and building systems measures

 Description of MeasureU Value of fabric element***Approx. cost based on typical 100 sqm Semi-detached house (incl. installation, excl. grants) Impact of Measure
Roof Replace any existing minera lis likely to have lost most of its insulating value, with 100mm of mineral wool packed between the ceiling joists with an additional 100mm dressed over the ceiling joists0.13 W/sqmK€800 / £585Improves baseline U-value by 96% taking BER/EPC rating from an F to E2
Solid Wall 150mm of external insulation applied to the face of the existing external wall with a polymer render finish0.14 W/sqmK€11,500 / £8,400Improves baseline U-value by 95% taking BER/EPC rating from an E2 to D1
Narrow Cavity Wall Pump the cavity with insulation beads and apply 125mm of external insulation to the face of the existing external wall and finish with a polymer render coating0.16 W/sqmK€2,100 / £1,540Improves baseline U-value by 90% taking BER/EPC rating from an E2 to D1
Windows & External DoorsReplace existing windows and doors with new triple glazed thermally broken units, installed and sealed with air tight tape.0.9 W /sqmK€11,500 / £8,140Improves baseline U-value by 80% taking BER/EPC rating from a D1 to a C
Floors Remove existing ground floor and replace with a new concrete screed floor with under floor heating, 200mm of insulation on a reinforced concrete floor slab on top of a radon membrane on compacted hard-core0.09 W/sqmK€5,500 / £3,895Improves baseline U-value by 94% taking BER rating from a C2 to a C1
Primary HeatingReplace with an air to water source heat pump with 380-420 per cent adjusted efficiency; it’s essentially that the HP is sized carefully to suit the dwelling* with two separate heating zones with both time and thermostatic control and independent water heating. €10,100 / £7,400Improves rating from a C1 to a B2/B
Secondary Heating SystemUpgrade to a high efficiency (min 76 per cent gross efficiency) stove that is suited to the room. Stoves should be as small as possible for the room, in this case it was 6.5kW. New ROI regulations (Part J) all but insist that you line the chimney before use.€2,500 / £1,770Improves rating from a B2 to a B1/B
Hot Water StorageReplace with factory insulation (50mm of spray foam applied to cylinder). €300 / £212Improves rating from a B1 to a A3/A
Solar Water Heating3.2sqm of solar heating panels installed on the southern aspect of the house.€4,500 / £3,300Improves rating from a A3 to a A2/A
LightingAll lights replaced with 100% low energy bulbs. Note that LED bulbs should only be purchased from well know lighting brands.€80 / £57Rating remains the same but overall energy usage reduced

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About Tim Lavin

Tim Lavin, B Arch Sc Dip Arch MRIAI, leads an award winning RIAI Registered Grade 1 Architectural Conservation Practice, Lavin Architects. Lavin Architects, 40 Mulgrave Street, Dun Laoghaire, Co Dublin, tel. 01 2845648

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