DESIGN & CONSTRUCTION
Does a Passive House have to follow a strict design style?
No. There might be an impression that Passive House’s have to be perfect cubes with no windows on the northern side, but this is not the case. It is best (most efficient and cheapest to construct) to create a compact shape (two storey is more efficient than a bungalow) with optimal solar gain, but the house designer should otherwise be free to create any bespoke design according to the Client’s needs. It is important that the Passive House concept can be adapted to local cultures, styles and building traditions.
Are south facing windows essential for the Passive House to work?
Not necessarily. Sure enough, it is ideal to have south facing windows to harvest the free energy provided by that great big furnace in the sky. However, it is also possible to achieve the Passive House standard if your site does not lend itself to maximising solar gain (but you will probably have to compensate for this with additional insulation). All designs have to be tested and verified in the Passive House Planning Package (PHPP) software. If you have a wonderful view from the northern side of your house, you needn’t deny yourself of this. The Passive House is not so strict as many people think.
Do I need a special site type if considering building a Passive House?
No, generally not. Of course, it is ideal to be able to design the building to face south, and to avoid over-shadowing by coniferous trees or buildings. However, if these conditions do not exist on your site, then don’t worry. Allowances can be made, and tested in the PHPP software, for any shortfall in terms of ideal orientation leading to reduced solar gain.
What is the best insulation to use for a Passive House?
There are no strict rules in this regard. The critical issue is to achieve the U-values (thermal performance) required as identified by the PHPP. Thereafter, you can use whichever insulation type you prefer or can afford, whether polystyrene, cellulose, polyisocyuranate, strawbale, sheep wool and so forth. Some insulation types are better performing than others, requiring thinner walls, whereas other are less efficient and will require thicker walls
Does a concrete house make it easier to achieve a Passive House?
Generally, yes. A passive house needs a lot more insulation than a typical house, and this is generally achieved by having significantly thicker walls. The thickness of walls depends on the U-values required which in turn is greatly dependant on the performance of the insulation, the type of construction (whether concrete or timber frame), overall design, orientation, compactness and so forth. You generally won’t notice the thick walls from the outside of the house, however, as the windows are placed in the insulation layer which is best placed towards the exterior of the building shell.
Must I use triple glazed windows in a Passive House in Ireland?
The safest answer to give here is Yes. All Passive House’s must be designed and tested using the specialist software PHPP and you might find, on occasion, that it is possible to use very high performance double glazing in some instances (though not necessarily throughout the entire house). If you do use double glazing, however, be aware that you will probably experience some thermal discomfort on cold winter nights whilst sitting close to such windows due to the temperature difference that will inevitably arise between the internal surface of the glass and the surrounding living space. Be aware that Passive House windows will take in more energy over the year than they let out (think about that for a moment ...), whereas the same cannot be said for even very high performing double-glazed windows. Lastly, did you know that double-glazed windows have been banned in Sweden since 1985?
Can I build a ‘Near-Passive’ house?
Yes, you can, but take care that you don’t fall short of imminent building standards to be introduced to Ireland. Some people find themselves reluctant to go for the ‘full’ Passive House option expressing a preference for what might be referred to as ‘near passive’. This is to be expected for some people who might be reluctant to consider something as new to Ireland as the Passive House standard, requiring air-tightness, triple-glazing, super-insulation, heat recovery ventilation and so forth. In principle, if people have their minds made up against Passive House standard (or indeed feel they can’t afford this standard), then there is little that can be done to convince them otherwise. It is important to think of the following, however. The DoE have decided that all new residential construction must be built to a carbon neutral standard by 2013 – that’s just four years away. Building a Passive House is perhaps the most economical method of achieving this standard, coupled with renewable energy technologies (such as a wind turbine or photo-voltaic panels). It makes little sense to knowingly build to a standard which will soon be outdated, likely adversely affecting property value in the future. Furthermore, if you build a ‘low energy’ house or ‘near-passive’, you will still need to install a heating system that is capable of providing good comfort in the worst possible weather (even if this lasts only a short period in the winter). This means that you will need a much larger heating system than you would if you build a Passive House, most likely requiring additional investment for that system. Further, energy prices are set to increase in the future, perhaps offsetting any saving that you might make in not building to the Passive House standard. In the end, making any improvements to a building in terms of energy efficiency will prove worthwhile and we recommend pushing your budget as far as you can to reduce your energy costs in the future.
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