Extremely economical passive houses - the future buildings, which after a decade, perhaps, may still be a novelty to the housing market and the demand for them will only grow.
A passive house instead of a three room apartment
Mindaugas is a future owner of a passive house in a Pilaitė district in the city of Vilnius. It has been a long road to owning a passive house. The idea for such house was conceived before the major economic crisis of 2008. The increase in a family of Mindaugas required a bigger living space. Back then, in summer of 2008, undecorated 3 room flat of 80 sq.m. was worth approximately 116, 000 €.
"It seemed to me that such price for an apartment is simply unreasonable. For a similar amount of money, excluding the plot of land, it was possible to build a house of 160 sq.m. However, the house had one major flaw – its heating was very expensive. Some of my friends and acquaintances spend 300 € or more on heating monthly. Therefore, I started to look for ways how to build a warmer building. In early 2009 I learned about the passive houses”, tells Mindaugas about his choice.
Like many other Lithuanians who reject everything new, Mindaugas felt suspicious about the idea of the passive house. It seemed to him that thicker than usual thermal insulation layers, special tightness of the building, ventilation ductwork system and no chimney seemed to him quite absurd, difficult and expensive to implement.
“I have decided that if I will ever decide to design and build a house, then it will be a passive house. However, back in the day, there were very few certified experts of the passive houses in Lithuania and they charged nearly 10,000 € for a project. Luckily, on the internet, I met people who helped me to make my dream come true.”
The more you eat, the hungrier you get
A small house project was designed by architect Aurimas Zaniauskas, calculations with PHPP (Passive House Planning Package) software were done by designer Karolis Januševičius. In autumn of 2012 first ideas were conceived.
On the basis of the first passive house built in Lithuania, the owner felt that in his future very warm and economical house it will be enough to lay the floor of 30-35 cm foam, make 30 cm Neopor layer on the walls and stuff the roof with wadding layer up to 40-45 cm.
“It turned out that I was wrong. After entering house data into PHPP program it revealed that energy demand for the building heating is 30 kWh / m². The situation was worsened by the fact that the house was being built on a small plot of 6 acres, so the heat of the sun was taken away by the neighbors living on the east and south sides of the house.
In the eastside, a neighbor's house on the hill obscures about 23 % of solar heat per year. There is no neighbor living on the southside but when the worst case scenario was simulated, the program has indicated that if such neighbor was present, then his house may consume up to 29 23 % of the solar heat. It is quite disappointing but you can’t really escape the circumstances”, Mindaugas recalls his disappointment.
During first calculations, it was not estimated that the small plot is not perfectly facing south. After corrections were done it turned out that home energy demand has decreased to 21 kWh / m². To continue to reduce home energy costs and to achieve the passive house standard was quite difficult, but the goal, however, has been finally achieved.
The weakest place in the house is the foundation
House of Mindaugas was supposed to be built on the flat foundation commonly used in passive structures, but he had to choose bored piles instead. This decision was made due to extremely unfavorable geological conditions.
"The tests showed that in one corner of the plot, harvested 40 cm from the surface, reached the required strength of soil, while the on the other side of the plot it would be necessary to dig into more than 2.5 meters deep. Moreover, there were large piles of sand poured out prior to soil removal throughout the entire plot. This means that sooner or later this vegetable soil will start to rot. Therefore, in order to make flat foundations we would have had to dig approximately 3 m deep pit, pour a lot of sand layers and densify them. It is a very expensive process. Due to additional soil work, the flat foundation could have cost me much more. I was afraid to take a risk and build a house on an uncertain ground.
Unprofessional builders are the worst enemies of the passive house
According to Mindaugas, design process of a passive house is easy and fun too. However, the fun ends when a building process begins. One of the biggest problems are possible building defects. Builders are used to building houses in accustomed manner and the fact that the passive house requires a very careful and precise work, is often a big surprise to them.
One house owner has already learned the hard way when he went away on holiday for a week and left company workers to insulate foundations without supervision. He returned and saw that they did their job so poorly that it all ended in angry and bitter break up. Work defects were removed and the insulation was thoroughly remade.
I’m glad I’ve decided to do additional insulation of poles. When I unearthed the foundation, I saw that it was poorly insulated. The foam was placed unevenly and slanted . Not only we had it all corrected, also we dug a meter in depth from the ground surface to additionally insulate the poles.
Of course, we have not managed to avoid heat loss through the poles, but their influence is reduced to a minimum. Overall, the biggest drawback of my house is its foundation, "- the owner admits.
Roof extrememly sturdy and warm
If the walls of the house are not special, they can be built from any materials and it is only important to properly insulate them. The roof, however, is a very different story. To properly insulate the roof, as in this case, it is necessary as much as 50 cm of thermal insulation material layer, and simple rafters are not the best option. Because, as we can all imagine, nobody produces rafters of such dimensions. An additional massive frame is necessary. However, in this case, the passive house frame will look too clumsy. For the roof, structures can be used IPE beams. Their height is 40 cm. So, you will only need an additional 10 cm tapping. Foundation of beams consists of pasted OSB sheets based between the two balks, which has much better heat conduction properties than wood, because the thermal material surrounds almost the entire beam. Only a very narrow part of the wood remains uninsulated. It is extremely important for a passive house because pure wood already creates some kind of thermal bridge.
"The wood is not as warm as foam or wool. Furthermore, these beams are lighter than conventional rafters and are just as strong, and the price was similar. It impressed me that it is nearly seamless factory system, not a manually assembled frame "- said the owner highly confident in his choice.
Other features of the house
Currently, Mindaugas is looking for windows best suited for this house. The market is full of various options but he would like to buy windows that are certified by Passive House Institute. He is also looking for a facade decoration, however, it bothers him the least. For roofing, he selected tiles, which decorate the entire house. The exterior of this house is dominated plaster and a few dozen square meters of clinker tiles.
The total area of the house is moderate -140 sq.m. By the way, this area size is no coincidence. Passive House Institute has calculated that the optimal area per family member is 35 sq.m.
"That is the exact total area. We decided to have an unheated shed and box room instead of a garage. In short, since our initial ambitions we have managed to save about 100 sq. m. of space which could have needed heating. It also saved us a significant amount of money, which we invested into thicker walls of the house. So, we have spent the same amount of money that we planned to”, - says a homeowner satisfied with results.
The heating system is the biggest headache for future inhabitants of the house. It is estimated that heating will require approximately 2100 kWh of energy per year. If the house is to be heated with electricity alone, it would fail to achieve the standard of the passive house, thus a different solution is required.
Homeowners are likely to refuse to use gas heating from the plot because this would be another source of thermal bridges. There are considerations to delegate heating and hot water production to heat pumps as they get energy from the air (“air-to-water "system) or the borehole (" water-water "system, commonly referred to as geothermal heating).The first mentioned system is more acceptable due to lower installation costs (approximately from 4000 to 6660 €) but its SPF (seasonal performance factor) reaches only 2,5 points.
Such heating is ineffective when the outdoor air temperature falls below -15 degrees Co. The other mentioned heating system costs more (from 7250 to 10100 €).
“Everything must be calculated very precisely. If any of the structures suffer from heat loss, then it is necessary to compensate for this in other parts. If one power source does not meet the needs, it is necessary to look for another. Above all, the goal is almost reached. The house will be really warm, stable and economical. The main thing - it will serve us, not vice versa. After all, these days we are so busy that after a day's work we have no wish to fiddle in the boiler room and perform minor repairs and the like. We have where to spend the money we earn. It is not for me to continuously invest into a house,” says the owner, speaking about the benefits of building the passive house and the future advantages of living in it.
The technical solutions applied by specialists that Mindaugas had selected are not the only ones that can apply passive house builders currently in Lithuania: the heat is supplied into buildings via underground tunnels (wadded underground pipes, so-called ground heat exchanger) already warmed air; solar collectors, the various uses of blinds, awnings, and canopies, tilting the solar rays, and so on. There are plenty of ways to achieve high energy efficiency. However, it is essential from the very beginning and plot selection, to talk with people who have complete and thorough knowledge of construction and building of the passive house.
Better health, favorable microclimate to live in, small bills and many situations that will no longer bother you - that's what you will get by choosing a passive house. Noisey neighbors, long power outages in winter will no longer be a problem because such house is capable of solving such problems autonomously.
These are requirements for Mindaugas’ house, so that it can meet the standard of the passive house with sufficient heating of 15 kWh / m²:
the floor must have a foam layer of 40cm (U – 0,091 W/m²K or R-10,99 m²K/W),
35 cm layer of Neopor on the walls (U – 0,082 W/m²K or R-12,19 m²K/W),
the roof must contain a 50-cm layer of mineral wool (U – 0,074 W/m²K or R-13,51 m²K/W),
house air circulation must not exceed 0.4 times per hour at 50 Pa pressure difference between the inside and outside,
recuperation efficiency factor - not less than 93 per cent,
Window thermal conductivity - not more than 0.8 W/m²K,
the extremely good tightness of the house is also necessary, with high-efficiency recuperation, the best windows and minimum amount of thermal bridges. NOTE. PHPP software indicates that heating 1sq.m. will require 15kWh of energy per year. This number is only forecasted. Calculations normally indicate that 20 Co temperature will be maintained during the heating season. If it will be higher, then energy demand will increase. Heating costs may increase due to often opening and closing of front doors.
Commentary of a specialist
Aurimas Zaniauskas, a certified passive house architect
The house of Mindaugas is nearly perfectly adjusted according to directions of the world. Implemented decisions were aimed at complying with the requirements for passive structures were dictated by the location of the plot. It is much more difficult and costly to do something useful in a house with its inner windows facing north. However, nothing is impossible.
What is the most difficult issue you came across in designing a passive house? What do you recommend for people who want a house of such type, what should be considered?
A lot of good information can be found on the internet, press or obtained directly from builders but it is often undigested. So, if a person is not a professional of the field (a builder) then this information will seem fragmented and it will be difficult to get a clear picture. The information in its entirety must be managed by the project manager with a team of certain specialists. The architect is especially important, other important persons are energy consumption calculator, constructor, heating and ventilation specialists. One can sense intuitively which project solutions is technically better but it’s the calculations that reveal how it is in the end.
When talking about the main principles in designing energy efficient and economical house, then it should be mentioned that it’s easiest to do it on the southward oriented plot of land with no shadows. Also, it is important not to forget to shade of windows
in summer time because glazed and uncovered large openings significantly increase the chances of overheating rooms. It is better not to include garage into heated area of the house. It is recommended to build a two-storey building with fewer corners, the shape of heated volume should be as simple as possible. Any possible thermal bridges should be avoided.
From a technical point of view, it is better to avoid ventilated facade finishing systems or mount them on fiberglass parts. The flat roof is particularly suitable and if you do a pitched roof then the better use of IPE beams. It leads to a much better thermal performance than using conventional wooden rafters. You need to make up your mind to buy more expensive windows - it is advisable to choose the warmest available. The recuperative ventilation system is necessary. Excessive heat insulation layer thickening is not appropriate. For example, a layer of walls thermal insulation materials can be only 30-35 cm. The thicker layer will not deliver any effect.
However, all this is only a series of well-known technical moments, which cannot be followed blindly.
It is important to remember that the goal is not to create a very cost-effective a thermos but a high quality of life in an efficient house. Also, it is important to keep in mind the aesthetics, proportions, and landscape. If the plot is located near the river or forest and has a great view to the north side, then you should not ignore it. It is also important to keep natural lighting indoor, the feeling of space, no matter how tempting it may seem to decrease the size of windows for additional savings in kilowatt-hours. Individual is the highest priority because the house is built for him.
It would be great if investors and planners could arrange south side plots in order to minimize the shadow covered area. Demand for such plots is growing rapidly.
Is passive house design work price significantly different from the currently popular B energy class constructed houses?
In order to achieve a high energy performance class, already during the design stage, it is necessary to calculate the energy consumption and adjust the solutions, taking into account the results obtained. Of course, the price will increase 10 – 40 % percent, depending on the complexity of the project. It is also important to note that it is appropriate to prepare heating and ventilation project parts simultaneously.
How long does it take to design such house?
If individual residential home energy costs are calculated during the design stage, then the process can be prolonged by 1-2 months. It becomes the additional part of the design project and architectural solutions have to combine and adjusted according to the calculations.
You have designed a number of energy-efficient houses. Have you managed to achieve similar results with the house of Mindaugas? If not, what were the obstacles?
Typically, our projected energy-efficient home energy consumption for heating ranges from 20 kWh / m² per year (extremely compact, close Cube-shaped two-storey or single-storey with loft buildings) to 35 kWh / m² per year (less compact form - the larger one-storey house ).This forecasted rate results from the calculation of costs performed during the design stage. In order to actually have such numbers, it requires a strict control of construction, building testing and maintenance. Currently, we are half way through the preparation of another individual house project, which aims to consume around 15 kWh / m² of energy per year for heating.
What kind of house according to energy costs by heating do prospective builders want?
When it comes to the energy-efficient house (not passive, with the precisely defined rate of not more than 15 kWh / m² of energy consumption for heating per year), it is desirable for it to use from 20 kWh / m² to 35 kWh / m² of energy per year for heating. Such indicators help to meet the requirements for buildings with A or even A + energy efficiency class. This is what I recommend to individuals currently planning the construction. However, it is necessary to bear in mind that energy-efficient homes are different due to sun-affected architectural solutions and they look slightly different.
I recommend to future residents not to be afraid of a more modern-looking building with large windows and systems that form shadows in the south and moderate walls in the north. In each case, the plot situation is different. That is why you should trust a specialist from the very beginning.
Commenrary of a specialist
Karolis Januševičius, a certified passive house architect
What heat source according to the price - benefit ratio is most efficient for tha passive house?
One correct answer does not exist, it depends on the specific situation. Building energy performance certification and energy efficiency planning defining the technical construction regulations limit certain choices. Geothermal heat pumps and biofuel boilers have more advantages than others.
Is it difficult to build a passive house? What are their requirements for Lithuanian climate, Vol. ie., what Thermal insulation material layers recommend floors, walls, roof?
A passive house, according to regulations of the German Passivhaus Institute, shall be called a house with a heat demand not exceeding 15kWh / m2 per year. Otherwise, it is not a passive house. These requirements depend on the climate.
The required thermal insulation thickness is determined by the form of the building, its orientation, the influence of drop-shadow "neighbors", static tightness level and ventilation system solution.
It is necessary to point out that energy consumption of the building for heating of the space is influenced not only by the thickness of thermal insulation partitions.
In very large quantities of insulation material, benefits of an additional layer are not proportional to the thickness of the attached material. In this case, the previously listed elements are very influential as well as linear thermal transmitters which are evaluated in each structural solution.
Since 2021 in Lithuania we will have to build only the A ++ class homes. Are their requirements are implementable?
A brief overview of these requirements is hardly possible. A or A + class parameters are actually implementable in residential buildings of one - two apartments.
To achieve passive house standard (15 kWh / m2 per year of heat for area heating), most of the criteria are met. A ++ standard provides additional requirements for buildings: to produce energy consumed by the building devices that use renewable energy sources must be installed.