DESIGNING FOR RESILIENCE iDEAL HOUSE AUCKLAND

Designing For Resilience Ideal House Auckland-Free PDF

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Building a Better New Zealand Page 2 of 11, In this paper we will detail the analysis process that was undertaken during the design process to. ensure that actual thermal energy demands match those that were predicted for the design. Figure 1 Rendering of the iDEAL House supplied by S3 Architects Ltd. The home is a rectangular shape with a second storey mezzanine for part of the plan area The. adjoining garage is outside of the thermal envelope and has been positioned such that it provides an. interesting form to the building without compromising the thermal or airtightness performance. The form of the house was the first key factor in ensuring good performance A simple two storey. rectangular form has a limited surface area for heat losses and containing a reasonable volume for the. internal spaces Having a surface area to volume ratio less than 1 0 ensures an optimised design. Reducing the surface area also ensures a more cost efficient construction there is less cladding area. material and other associated material volumes such as insulation linings paint etc A larger surface. area would also have required a portioned increase in the levels of insulation required for the building. to make up for the increased heat losses heat loss being directly proportional to surface area. PASSIVE HOUSE CERTIFICATION, A Passive House is well planned during the detailed design phase however the certification of a. building is undertaken at the completion of construction The process involves a combination of on. site quality assurance checks together with a review of the as built design details product data sheets. analysis reports and calculations These are compiled by the Passive House Designer and are. submitted to an independent Passive House Certifier for verification. The core performance criteria for a Certified Passive House. Meeting an envelope airtightness level less than 0 60 air changes per hour ACH at 50. Pascals pressure differential This is tested on site at the project completion through a Blower. Door test under both pressurisation and depressurisation in accordance with Method A of EN. The specific heat and cooling demand is to be less than 15kWh m2 per annum The New. Zealand Building Code8 has no specified performance benchmark for New Zealand homes. however from experience we believe that the average modern code minimum home in. Auckland would have a specific heat demand in the order of 40 to 50kWh m2 per annum. Thus a Certified Passive House would have a performance improvement of around 60 to 70. to the average code minimum home in the region,The heat load must be less than 10w m2. 28 May 2014,Building a Better New Zealand Page 3 of 11. The primary energy demand must be less than 120 kWh m2 per annum. Using a balanced heat recovery ventilation system with a least 75 efficiency through the. heat exchanger A large number of heat recovery ventilation systems have been independently. tested by the Passivhaus Institut and are Certified Components Using Certified Components. means that no additional documentation needs to be supplied to verify compliance and the. performance of the system is guaranteed, Having an essentially thermal bridge free construction so that the specific heat energy demand.
criterion is achievable and to keep internal surface temperatures well above dew point. temperature This is essential to ensure there is a condensation and mould free construction. Ensure the building envelope is not at risk of interstitial condensation. The bulk of these calculations are completed in a spread sheet developed by the Passive House. Institute called the Passive House Planning Package PHPP 1. Thermal bridging calculations are prepared using isothermal analysis software called Psi Therm4 that. enables the calculation of the thermal bridging coefficient or factor These are subsequently input. into the PHPP1 Checks on the building envelope details for the transfer of water vapour and. condensation risk are conducted through hygrothermal analysis using WUFI Pro 5 03. THERMAL MODELLING,Passive House Planning Package PHPP 1. PHPP uses an energy balance method as the basis of verifying that the Passive House Standard has. been met PHPP is regarded as being highly accurate up to 0 5kWh is claimed and has been. repeatedly verified through validation using dynamic simulations as well as testing of actual realised. buildings through meticulous measurements over several years. The tool is based on physical principals using European norms calculating heating cooling and. primary energy demand as well as determining summer overheating periods We have also undertaken. independent verification using Integrated Environmental Solutions Virtual Environment IES. VE 2 thermal analysis of the building envelope to establish specific heat energy demand. The climate data set for the Auckland region is now pre loaded in the latest version of PHPP8 5 This. data set originated from IWEC International Weather for Energy Calculations from ASHRAE and. was compared with NIWA data The data set was independently tested by the Passivhaus Institute. Opaque components, The U Value calculations for the opaque building elements are based on International Standard ISO. 69469 There are a number of notable differences with this standard compared with NZS4218 200911. that are worth discussing, ISO 6946 uses a slightly different set of interior and exterior surface resistances offering more. alternatives of heat flow scenarios that are ore realistic for heat loss calculation. Any cladding to the outside of a ventilated cavity is excluded from the U Value calculation. unlike NZS4218 which uses a method of de rating those layers ISO 6946 allows still areas to. be considered however a vented cavity should not be considered still air. The final U Values calculated for the iDEAL house are tabulated in Table 1 based on ISO 6946. Table 1 Opaque building component U Values from PHPP compared with minimum NZBC8 R Values. Element U Value W m2K Total R Value m2K W H1 minimum code. R Value m2K W,Ground floor 0 433 2 31 1 3,Exterior walls 0 282 3 54 1 9. Southern exterior wall 0 209 4 78 1 9,Roof 0 183 5 46 2 9.
Mezzanine overhang 0 208 4 81 1 3,28 May 2014,Building a Better New Zealand Page 4 of 11. The areas of each of the building assemblies are tabulated in the PHPP and the respective heat losses. are calculated We have made a comparison using NZBC H1 minimum code requirements in Table 2. and we can see there is a 53 reduction in heat loss of the opaque building components compared. with a code minimum home, Table 2 Opaque building component heat losses compared with minimum NZBC levels. Element Area m2 Element Heat loss H1 minimum code,W K heat loss W K. Ground floor 163 3 70 7 125 6,Exterior walls net 216 32 61 0 113 9. Southern exterior wall net 29 51 6 2 15 5,Roof 186 34 0 64 1.
Mezzanine overhang 6 25 1 3 4 8,Total 173 2 323 9, The PHPP element areas are measured using exterior dimensions using the convention given in ISO. 1378916 This yields a more conservative result as there is a degree of double measurement at the. junctions and corners Junctions have slightly larger heat losses due to geometrical thermal bridging. To adjust for the thermal bridging that occurs at the junction of elements a thermal bridging coefficient. is calculated using Psi Therm in accordance with ISO 1021110 and is entered into the PHPP. together with the respective lengths of the thermal bridges As there was some conservatism in the. measuring of the overall element areas taking the thermal bridging effects into account will often. reduce the total heat loss so long as the proposed junction detail is sensible. For example the external roof barge was calculated to have 0 199 W mK with a length of. 61 2m this results in a heat loss reduction of 12 2 W K Examples of this calculation are discussed in. more detail further on in this paper, Heat losses through the ground follows the EN ISO 1337013 standard taking building geometry into. account The larger the floor slab the lower the heat losses are due to the insulating effect of the soil. Seasonal ground storage effects are also included in the calculation as it separates heat flow into. steady state and harmonic components, The windows selected for the iDEAL house are a Passive House Certified Component This means the. windows can be easily selected from the list of components and performance data is pre filled in the. tables Aluplast PVC windows with ClimaGuard triple glazing were selected for the project This has. glass U Value 0 69 W m2K frame U Value 0 81 W m2K and edge spacer 0 027 W mK. The total window area is 84 58m2 with a ratio of glazed area of 55 87m2 and frame area of 28 71m2. The breakdown of heat losses through the window components as determined through PHPP is given. in Table 3,Table 3 Window component heat losses,Glass W K Frame W K Spacer W K Installation W K. South 1 10 0 97 0 29 0 43,East 9 99 7 00 2 05 2 57.
North 10 9 6 03 2 68 1 90,West 16 6 9 26 1 76 2 60. Total 38 6 23 3 6 78 7 5, Total window heat loss 76 18 W K and the total average window U Value 0 90 W m2K or R. Value 1 11 m2K W using ISO 10077 1, When comparing with minimum H1 requirements from the New Zealand Building Code we only need. a window R Value of 0 26 m2K W giving a heat loss of 325 W K Passive house windows for this. example offer approximately 77 reduction in heat losses compared with a standard aluminium. window with double glazing The windows are where a Passive House makes significant performance. improvements,28 May 2014,Building a Better New Zealand Page 5 of 11. We note that NZ4218 takes a highly simplified approach to window losses where many variants are. not taken into account This subsequently leads to a higher level of inaccuracy which is problematic. when analysing energy efficient buildings The effect of the spacers and installation thermal bridges. can be significant, Consider if standard aluminium edge spacers were used in the iDEAL house windows the heat losses.
for this element would increase from 6 78 W K to 27 9 W K This is greater than the heat losses. through the PVC window frames This indicates that to obtain a return on investment on any thermally. broken frame a high performance glass edge spacer is essential. Certified Passive House windows consider more than just the thermal and airtightness properties The. hygiene requirement restricts the minimum interior surface temperature on the window This is to. ensure that condensation cannot consistently form on the windows that subsequently leads to mould. growth The relative humidity in either the window material s pores or directly on it s surface cannot. exceed 80 This ensures a healthy living environment. The other requirement is for comfort This restricts the average indoor temperature to the minimum. surface temperature of the window by a maximum of 4 2K With a 20oC indoor operative temperature. environment the window surface temperature must effectively not fall below 15 8oC This ensures. there is no downdraft effects and no perceptible radiant heat deprivation and thus there is a. comfortable living environment, The New Zealand Building Code Clause E26 has a prescriptive approach to the installation of windows. as a measure to prevent water ingress from wind driven rain Ironically the windows have large. thermal bridges which causes condensation on the interior face of the window components during. winter months In many cases if the thermal bridging was addressed and the window was installed in. an airtight manner the moisture issues could be eliminated. Having to install the windows to New Zealand Building Code requirements meant that the installation. thermal bridging effect was exacerbated We used a higher performance frame than would normally be. required to overcome this performance limitation The PHPP assumes a very conservative installation. 0 04 W mK as default with the worst case always occurring at the window or door sills. Uncertified windows would require calculation of the frame U Value to be determined based on ISO. 1007714 similar applies to the glazing U Value together with the edge spacers and installation thermal. bridging co efficient Analysis to check the hygiene and comfort requirements should also be. undertaken We initially worked through such calculations using thermally broken aluminium window. suites for the iDEAL house However the restrictive nature of how the window had to be installed. meant that we could not meet the hygiene or comfort criteria necessary for Passive House. Certification We therefore moved to using an imported PVC window frame that was Passive House. New Zealand aluminium window manufacturers are only just starting to adopt ISO 10077 for the. calculation of the window component U Values this will allow a more consistent approach and allow. performance to be properly compared with overseas products So far the fabrication and installation of. locally manufactured aluminium framed windows has not been consistent enough for us to be. confident that they could always meet the airtightness requirements for a Certified Passive House. To ensure solar gains are accurately calculated in the energy balance shading effects are taken into. account This includes eaves screening devices and overshadowing structures and topography. Heat Recovery Ventilation, Although not directly related to our analysis it is wort. DESIGNING FOR RESILIENCE iDEAL HOUSE AUCKLAND PAULA HUGENS BE MIPENZ CPEng CEPH 1 DENISE HENKENHAF 1 1 eZED Limited 3 70 Glenda Drive Frankton Queenstown ABSTRACT The iDEAL house is a private family home located in suburban Auckland and due for completion in July 2014 The design brief by the client asked for a highly energy efficient

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