The NuTech Passive Solar House Concept is a little different. It was devised originally by Mark Forkin and Bill Quigley out of the design and systems used in the original Passive Solar House in Knocklyon. All of the technologies developed have been rigorously tested over the past 20 years.

 

In essence, the U-Values arrived at are a little higher in certain circumstances over the PHI values to ensure cost breaks are achieved and then this is compensated for by way of a larger solar array of Evacuated Tubes delivering energy into the HRV system even in cloudy weather (hence the reason for using evacuated tubes over flat plate collectors).

 

The thinking is that as insulation levels get higher and higher it is a clear case of diminishing returns which are, as mentioned, offset by the amount of energy delivered to heating by way of the solar array. NuTech are in full agreement that high levels of airtightness are essential. The reduction in Thermal Bridging is also vitally important as this has an enormous effect on the overall Heat loss Characteristic (W/K) of the house.

 

 

Typically, the NuTech requirements for the fabric U-Values must be less than or equal to the following:

 

 

 

                                    U-Value (W/m2.K)

Ground Floor                            0.12

External Wall                             0.16

Roof                                            0.14

Windows and Doors               1.20

 

Infiltration Level                        1.0 ACH at 50Pa

 

 

  

As can be seen there are four essential differences to the typical PHI requirements:

 

Ø      The first is the External Wall U-Value – this is raised to 0.16 W/m2.K as it can be achieved in timber frame with a reasonably sized stud which then has internal insulation fixed to reduce the effect of thermal bridging.

 

Ø      The second is the Window U-Value – this is raised to 1.2 W/m2.K as it then allows the use of well designed double glazing rather than the more expensive triple glazing unit.

 

Ø      The third is the level of Air Infiltration – this value has been raised to 1.0 ACH at 50 Pa. A difficult but more achievable target which also helps reduce construction costs.

 

Ø      The fourth item is that energy from at least a 6m2 Evacuated Tube Solar Array is INTEGRATED into the HRV system, thus solar heated air is being circulated to all rooms within the house even in dull weather. The heat generator, whether it is an internal wood pellet boiler or an air to water heat pump is also integrated into this system. This fully integrated system is controlled by way of the NuTech Intelligent Renewable Energy System (IRES) controller 

  

 

 As regards Thermal Bridging, systems have been developed with the timber frame company KTF Ltd such that the amount of thermal bridging is hugely reduced by way of the insulation systems and particularly by way of details around the windows and doors. As mentioned previously, this is vitally important. It is worth remembering that if the Thermal Bridging factor in the DEAP analysis is 0.08 W/m2.K then the U-Value for all of the elements is increased by this amount i.e. a wall U-Value of 0.16 W/m2.K becomes 0.24 W/m2.K in the overall calculation. It is that serious.

 

 

Photo 3: A NuTech / KTF Passive Solar House at Dunleer, Co Louth

 

 

The NuTech Passive Solar House system has the following features:

 

Ø      It has reasonably low U-Values for all of the fabric items

 

Ø      It is tested to achieve less than 1.0 ACH at 50 Pa

 

Ø      It integrates the energy from the solar array into the HRV system.

 

Ø      It integrates energy from the back-up boiler (internal wood pellet or heat pump) into the HRV system.

 

Ø      There is also a facility to have filtered recirculated air within the system thereby allowing 5 kW to 10 kW of heat to be distributed around the house, based on the size of house. This greatly improves the Thermal Response of the back-up heating system should it be required.

 

Ø      The system is designed to meet the requirements of the Draft Part F of the Irish Building Regulations.

 

Ø      A unique feature is that during periods of higher levels of solar radiation more fresh air is brought in by way of the HRV system to ventilate the house to a higher level than required by the Building Regulations to maintain freshness within the house. This can be done as it is using the solar array to its optimum level and the house is being either heated or ventilated at a zero energy penalty.

 

Ø      A higher percentage of the domestic hot water will be achieved by this system than with the smaller array on the normal Passive House because there is twice the area of solar collector.

 

Ø      The NuTech Passive Solar House is designed to achieve an A2 rating on SEI's BER scale

 

A significant point with the NuTech Passive Solar House is that SEI's DEAP calculation method allows the designer to take into account the energy from the solar array that is being transferred to reduce the Energy Demand for Space Heating. This improves the BER rating of the NuTech Passive Solar House and aids the achievement of an A2 rating.

 

 

 

Photo 4:           A NuTech Passive Solar House built for Fingal County Council in Oldtown, Co Dublin

 

Further Information

  Please contact NuTech Renewables Ltd for further Information