Just to continue what I started in June of looking at various decision points along the way & the conclusions we've come to.In part w of Passive House Design & Construction decisions I will be highlighting the following areas: Window Cills, Heat Recovery ventilations ( MHRV) , Boiler Plant Room Location & Skimmings vs Tape & Fill.
Window Cills - usually in Ireland these are concrete or granite, and are supported by the external blockwork. However the catch is that we'r using a renderboard so that load bearing structure is not there. In short this leaves 2 viable options - either metal or a lightweight plastic. We choose powder coated cills in the same colour as the windows.
Pros : no maintenance, drip from cill extends beyond building Cons : get scratched during construction, cannot be stood on
Heat Recovery Ventilation - houses generally have vents in the walls, trickle vents on windows or a central MHRV unit. The use of these units draw quite strong opinion from people based on their experience or not. The topic has been well flogged on many forums but is basically a requirement for a certified Passive Haus. The trick here is not to turn it on until the house is dust free lest dust be draw into the ducting. Space has to be left for the ducting in the building structure in order to keep it big ( & therefore with low velocities and noise). These systems need to be properly sized, designed, installed & commissioned. Many cheaper units are not as efficient and hence use more electricity to run.
Pros : better air quality apparently ( its filtered entering & leaving the house)., lower heating bills Cons : expense
Boiler / Plant room location - In many houses this is simply a back room where the equipment ( boiler / tank ) etc... are jammed in. In many countries the basement is used. In our case we've chosen to go with putting much of this in the garage. In addition I've heard it recommended to put the tumble dryer ( if you have one that is) out in the garage as they are a significant source of fires / smoke damage in domestic houses.
Pros : garage space per square meter is about 65% cheaper ; Cons : longer pipe runs
Skimming ( plastering) vs tape & fill - this is another chestnut where people have either had great or awful experience. The usual approach in this a wet plaster skim over plasterboard - in the future if you want to put up a picture frame or similar then you have to find the stud behind as the plasterboard is not weight bearing. The results is highly dependent on the skill of the plasterer obviously. The tape & fill approach ( not widespread in Ireland) uses sheets of a dense load bearing material such as fermacell with the joints between sheets filled. I have heard that this not as skilled a job & the results a lot more variable / inconsistent. We ended up going for skimming.
Pros : with a good plasterer the finish is perfect. Cons : more expensive, regular plasterboard is not load bearing, wet plaster introduces water to the building which has to dry over about 4 weeks.
In further blog postings we'll at other design & construction decisions in more detail, bearing in mind that many of these are indeed relevant to any new house build, not just a passive house.
Window Cills - usually in Ireland these are concrete or granite, and are supported by the external blockwork. However the catch is that we'r using a renderboard so that load bearing structure is not there. In short this leaves 2 viable options - either metal or a lightweight plastic. We choose powder coated cills in the same colour as the windows.
Pros : no maintenance, drip from cill extends beyond building Cons : get scratched during construction, cannot be stood on
Heat Recovery Ventilation - houses generally have vents in the walls, trickle vents on windows or a central MHRV unit. The use of these units draw quite strong opinion from people based on their experience or not. The topic has been well flogged on many forums but is basically a requirement for a certified Passive Haus. The trick here is not to turn it on until the house is dust free lest dust be draw into the ducting. Space has to be left for the ducting in the building structure in order to keep it big ( & therefore with low velocities and noise). These systems need to be properly sized, designed, installed & commissioned. Many cheaper units are not as efficient and hence use more electricity to run.
Pros : better air quality apparently ( its filtered entering & leaving the house)., lower heating bills Cons : expense
Boiler / Plant room location - In many houses this is simply a back room where the equipment ( boiler / tank ) etc... are jammed in. In many countries the basement is used. In our case we've chosen to go with putting much of this in the garage. In addition I've heard it recommended to put the tumble dryer ( if you have one that is) out in the garage as they are a significant source of fires / smoke damage in domestic houses.
Pros : garage space per square meter is about 65% cheaper ; Cons : longer pipe runs
Skimming ( plastering) vs tape & fill - this is another chestnut where people have either had great or awful experience. The usual approach in this a wet plaster skim over plasterboard - in the future if you want to put up a picture frame or similar then you have to find the stud behind as the plasterboard is not weight bearing. The results is highly dependent on the skill of the plasterer obviously. The tape & fill approach ( not widespread in Ireland) uses sheets of a dense load bearing material such as fermacell with the joints between sheets filled. I have heard that this not as skilled a job & the results a lot more variable / inconsistent. We ended up going for skimming.
Pros : with a good plasterer the finish is perfect. Cons : more expensive, regular plasterboard is not load bearing, wet plaster introduces water to the building which has to dry over about 4 weeks.
In further blog postings we'll at other design & construction decisions in more detail, bearing in mind that many of these are indeed relevant to any new house build, not just a passive house.
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