From the outset we knew we wanted our new home to have lower running costs than the old one. as well as the apparent financial advantages, there is an environmental imperative for us all to use less energy too.
There are numerous standards and buzz words surrounding this area, Zero Energy, low Energy, Zero Carbon and Carbon Neutral for example. A new standard that’s taking off in this part of the world (it’s already a requirement in the Republic of Ireland), is ‘nearly Zero energy Buildings’ or nZEB.
But Passivhaus (Passive House) was the one we knew many about and it seems to be well recognised when you are talking about the specifications for a new self-build. However, numerous companies we talked to, including window producers and energy consultants, cautioned us on the idea of going for a fully certified Passive house build.
This wasn’t because they thought a Passive house is a bad idea, on the contrary, but the phrase ‘diminishing returns’ was often quoted, while pretty much everyone widely agreed that we ought to still try to adopt the main principals for our own bygga.
Passive Principles
So let’s look at those principles. Here’s a slide from a talk I attended showing the 5 main principals of Passive House.
Very High Levels of InsulationPassive houses are very insulated.
Thermal Bridge totally free ConstructionTheir design and building methods eradicate junctions where a conventional building conducts heat away.
High performance Windows / FramesPassive house windows are triple glazed and the frames and fittings are all made for an ultra-low U value. In addition passive houses take advantage of solar acquire using south facing windows.
Airtight building FabricThese houses are airtight, eliminating the conventional ‘drafty’ buildings of old. A passive house should not leak much more air than 0.6 times the total house volume per hour.
Mechanical Ventilation System with heat RecoveryBecause these homes are air tight they need mechanical ventilation. These systems expel the stale air and moisture, replacing it with fresh air. This process happens across a heat exchanger so up to 85% of the heat is retained.
Design
While it’s possible to build a fully certified passive home in the style we wanted, it is much more challenging and certainly much more expensive.
As an example, one builder we spoke with that had just completed a certified passive house told us certain design elements (like dormer windows) were much harder and much more time consuming to build and thus much more expensive to achieve in a certified Passive House. While we want low heating costs for the new Automated home 2.0, we didn’t want that to be at the expense of our design and other features.
Masonry Construction
The 2 main passive house projects that I followed online (Ben Adam-Smith and Portree Passivhaus) had both gone for masonry construction.
Our last house had stud walls upstairs and a wood first floor which we always regretted as both were very noisy. So best from day one our wish list had been set out for solid walls and floors and we also spec’d concrete stairs to be sure of no squeaks or creaks there either.
That sound issue did colour our opinion on building wood frame too. Although having seen a beautiful wood frame home, recently built by a close family member, I’m sure that we could have been pleased with one too.
Carbon for Build
Not going TF also implied having much much more concrete in our build. There are massive amounts of embodied energy in many building materials – like steel and glass for example, although this will improve over time as much more of our electrical power comes from renewable sources. Concrete uses a chemical reaction called “calcination” that takes place during the process of making ‘clinker’, a important part of concrete, that splits the material into calcium oxide and CO2 (here’s a good short article from the BBC on concrete production). new methods are appearing that are improving the CO2 emissions for concrete production so things ought to improve here too in the future.
Interestingly the passive standard has absolutely nothing to say on the subject of decreasing the carbon during construction. Its only issue is creating a building that won’t require much energy once built.
We used a fabric first method and our block build, plus stone wall, tiled floor and overhang in the barn helps to soak up heat from the winter season sun and release it back into the house. We’re also running the heat pump much more at night on our less expensive economy 7 electrical power tariff and this is all working well. We got a 1.9 airtightness test rating in the end and our heat Pump and MVHR are working well together to offer a very comfortable environment. I’m recording data for the year and ought to have an update sometime in January on our energy usage for 12 months.
Budgets & Compromise
As with so much in lifeDessa beslut var en tightrope promenad mellan de konkurrerande kraven att behålla vår utvalda design, våra krav på en låg energibyggnad och vår ändliga budget.
Några av våra val har kommit ner till återbetalningstid. Om kostnaden för att gå från dubbel till tredubbla glasfönster tar, säger 15 år att återhämta sig genom något lägre värmeräkningar, då skulle du välja det? Om det är 30 år istället då vad sägs om nu? Den punkt där dessa saker är vettiga kommer att variera för individen. Att säga att jag tror att det viktigaste kompromissen i hela vårt projekt har varit våra fönster och måste träna för dubbelglas i stället för trippel.
Vi vill också ha ett Solar PV-system, men det måste vänta. Det är synd att det finns noll incitament i norra Irland för värmepumpar eller sol PV etc. Jag tror att vi är den enda delen av Storbritannien och Irland att inte ha någon. Eventuellt kommer den nya energitekniken för NI att komma senare i år att ändra det.
Eftersom dessa byggmetoder och produkter blir mycket vanligare här kommer förhoppningsvis att priserna falla. Om vi började igen på morgonen är jag ganska säker på att vi skulle gå till och med ännu mer mot den passiva standarden än vi har gjort.
Efter att ha bott i huset i mycket mer än ett år nu är vi väldigt nöjda med att vårt beslut inte brinner någonting var den bästa.
Låg energi?
[Uppdatering – Här är siffrorna för våra första år som körs]
Låg energi? Eco House? Dessa termer är inte väldefinierade. Men vi har ett hem som åtminstone är riktigt välisolerat, utnyttjar Solar Acquire på vintern, använder ett intelligent bygghanteringssystem, körs endast på el, har en bra termisk massa och slutligen stor komfort och luftkvalitet nivåer året runt.
Nästa gång
Nästa gång vi kommer att titta på en del av den nya tekniken i det automatiska hemmet. Under tiden kom ihåg att kolla in vårt Instagram för att följa projektet, läs resten av de automatiska hemmet 2.0 bloggmeddelanden och hitta länkarna till alla produkter som vi har använt i vår självbyggnad.
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