Passive House Module; Blog Assignment 2

Report Title: Economic Analysis of passive houses and low-energy houses compared with standard houses.

Authors: A. Audenaert, S.H. De Cleyn, B. Vankerckhove (2007)

This study investigates three different buildings types, the Passive House (PH), the Low-Energy House and the Standard Traditionally Built House. The paper begins by introducing the drivers and need for these more energy efficient dwellings which include the global warming epidemic and protocols such as Koyoto. It is stated that the potential GHG emissions reduction in the housing sector from an economic point of point of view is what will be addressed throughout this paper. This is to be done by carrying out an economic analysis on the three previously stated house types.

The first details which were stated in the report were what house types were to be used. It was decided that five different types of PH were to be used along with three different types of low-energy and standard houses. All of these houses are to be exactly the in same geometry and size to each other with the only difference being the materials used in constructing them. All of the various different materials were all shown in a table detailing all the different specifications and construction types. In terms of energy cost analysis two different types of data and calculations are presented, these being at constant energy costs and growing energy costs. All of this analysis also takes into account specific surplus costs during building, possible subsidies and potential energy savings over a 20 year term.

Through this analysis it is shown that the break-even time for a low-energy house compared with the standard house is 12.3 years and 29.9 years for the PH at constant energy prices. In terms of growing energy costs the time needed to recover the greater cost of a PH is 18 years in comparison to a standard house and 9.5 years for a low-energy house in comparison. This also states that when comparing the PH to the low-energy house the break-even time is 24 years.

There is also a cash flow analysis in this report which tries to predict the evolution rate of a variable mortgage for the coming 20 years by using a fixed rate. In this section three separate comparisons are made: Standard to low-energy, standard to PH and low-energy to PH. This analysis was also carried out in two parts, constant energy costs and growing energy costs. The results from the constant energy costs are clearly in favour of the low-energy house after the initial additional costs have been incurred and spread over the 20 year period. In assessing the cash-flow analysis in terms of growing energy costs three scenarios were simulated. These included annual growth rates of 5%, 10% and 15%, with the figures in the tables being ones which show the impact on the annual family budget for each scenario.

One of the most important factors detailed in this paper is the fact that the more energy prices increase, the more the impact of the PH becomes positive. This is very apt at this moment in time in the current climate of constantly increasingly energy prices. Comparison of the low-energy house with the PH demonstrates the profitability of the low-energy house after 2 years. The PH is only profitable in cases where the growth of energy costs are higher than 10% and is only more profitable than the low-energy house if the growth is more than 15%. The low-energy house is profitable in all cases in comparison with the standard house.

Overall the analysis shows the break-even time is always shorter for the low-energy house than for the PH over the period which was analysed. Nevertheless it is very dependent on the growth of energy prices. The cash flow results show that the low-energy house is the safest choice with a minimal impact on the family budget considering constant energy prices. The impact of the PH is strongly dependent on the evolution of the energy prices and needs more time to break-even to begin paying back than the low-energy house. The final conclusion and finding of this paper which was presented was that as the energy price and growth rate is so unpredictable, at this moment in time the low-energy house is the safest choice at this moment in time because the profit is less dependable on an irregular variable.

Please feel free to comment on or ask questions about what it written above or the report in general. I would be glad to answer any questions or queries that you may have or more information which may be wanted.

Case Study, Blog Assignment 1.

This case study is based on a Passive House which was the first to be constructed and certified in 2009 in the ile-de-france region of the country. The house is located in a town called Bessancourt which is situated around 28km from the french capital Paris. The house was designed and constructed by Karawitz Architecture and not only meets the passive house standards but also adhere's to many sustainable guidelines.

North Elevation (inhabitat.com)

Aesthetically the structure is an abstract replica of a traditional house which drew inspiration old barns which would be quite common in the part of France in which it is situated. The entire structure is created from the assembly of large solid wood panels which were prefabricated off site. The unique second skin of the building is one which is not commonly seen in construction as a whole. This skin is made from untreated bamboo which envelopes the solid wood frame, passing through the windows to the north and finishing by unfolding onto the roof. To the south of the structure identical bamboo shutters are fitted onto the large open bay windows providing both shade and light, during both day and night. This cladding over time will eventually turn a grey colour and not only helps in reaching the required standards but in also adding a sustainable element and natural look to the overall building. In terms of the overall cost of the structure, according to the Passive House Institute data base the figure was nearly €290,000. This price in terms of buying a house in this region at the same time is very advantageous, with the passavie house coming in considerably cheaper.

 

Bamboo Outer-skin Layer (solarpedia.com)

The structure has a floor area of 161m sq and has only one concrete element in its make up, that being the ground floor slab. External wall construction as mentioned before is made up of two layers, compromising of the bamboo skin and hard wood panels. Along with this there is an under roof membrane, wood fibre insulating boards along with an airtight steam brake which all aid in insulating and improving air tightness in the structure. When looking at the different U-values of this building it can be seen from those given on the passive house data base that they are a little bit higher than those of Ireland’s first passive house which was built in 2005. However even though this is the case the heat load of both structures is calculated at 13 w/ (m2). In terms of the primary energy requirement which is required to be under 120 kWh / m2a, this building comes in at 90 kWh / m2a in comparison to the Irish example which has a lower requirement of 76 kWh / m2a.

South Elevation (inhabitat.com)

While it is important to compare these two types of structures as they come under the same classification it is important to take some factors intp account when comparing. They are both certified passive houses but are both completely unique designs which have been constructed using completely different materials and are both operating in very different climates. I do however think that this passive house in Bessancourt has included an aspect of sustainability which up until now has not been seen very often in the passive housing area.

Passive House Module, Blog Assignment 1

For my first blog assignment case study I have chosen a recently constructed passive house in Bessancourt, in France.... Blog to soon follow..stay tuned

Irelands first Passive House, 'Out of the Blue'

Out of the Blue was constructed by Tomas O'Leary of Mosart Architects in 2004. The house is  a 4,000sq foot two storey split level house which is located in the garden of Ireland in Co. Wicklow and is the home of Mr. O'Leary and his family and was constructed in Ireland at a time the passive house concept was not very well known. The house maintains a high level of comfort throughout the year using just 10% of the energy of a conventional house, achieved through high levels of insulation, southern orientation, air-tight construction and mechanical ventilation with heat recovery. The latter refreshes the air in the house 12-times daily, so the house is also very healthy. As the house is a lived in family house and the first of its kind in Ireland it has naturally received huge public interest and its associated details can be seen on the Mosart website.


'Out of the Blue'-Irelands first Passive House

The construction of this house using these methods was revolutionary for the Irish construction industry and increased the interest in this building methodology while showing potential clients that it is in fact possible, comfortable and affordable. The building is also not one which is visually polluting and in fact has the look of a normally constructed house. There are however many different technical and construction details which were and are to this day used in the running of the building. The house has a constructed outer leaf of block cladding with 315mm of EPS insulation which can be seen in-situ in the linked Construct Ireland article. Some of the other details of the construction include the house being south facing, having a heat recovery ventilation system which is certified >90% which was supplied by Produkt Ltd and also having 7.2m sq of solar supplied by Eco-NRG Wexford. There is also much more technical data which can be seen in the technical overview of the house supplied by Mosart and an associated project data sheet which is available from the passive house insitiute online. Both of these pieces of information give all the relevent information in regards this build including u-values and appliance information along with the companies who supplied and installed them. Another great aspect of this build is that most of the fixtures and fittings were all supplied form Irish companies showing that we have had and currently possess both the knowledge and technology to fully introduce and adopt the house in the Irish construction industry.   


First Steps

The Passive House (PH) technique is fundamentally a method rather than a specific building style. While several PH building techniques have been developed to suit the European climate it is important that these are not just copied without assessing and developing a specific solution for each area and climate. This is because of the massive differences in elements such as solar gain between different climates, e.g. Sunny California and Dreary Galway. While the climate changes the concept and laws of physics remain the same around the world in different climates. Although the designs of PH may appear quite different, the principle remains the same of reducing investment through energy efficient design (Lovins). When the heating load is less than 10 W/m2, independent of climate, the ventilation system can easily be used for space heating and then a separate heating system is no longer required. While there is an associated extra capital cost during the construction stage of PH compared to traditional methods the costs would rise much more dramatically if the goal was to achieve a 'Zero Energy House' instead of a PH as well as there being almost no additional environmental benefits. These PH's have a very low energy demand for maintaining interior comfort in the heating season. Examining the heating load is just one example in other regions other energy services may be of greater importance than that of heating. As stated earlier it is important to investigate the specific PH solution for each separate project with each one being different and unique. In this case the different technologies available, ventilation systems for thermal comfort and various other associated methods should all be investigated. There are also some rules of thumb to be followed, such as

Keeping Comfort to a high level.
Solutions should be simpler than what is used conventionally.
Insulation is highly recommended in all climates.
Shading is paramount in all climates with high radiation levels.
Heat recovery is necessary in all climates be they hot or cold.
The use of very low auxiliary energy is of great importance.
And in Many cases the ground may be used as a heat or cold buffer.

After defining the goals in different climates the next step is to perform a 'computer based parametric study' of the design solutions and to check the results. A traditional building design can be used as a starting point, then each element can be modified step by step.