Automated home 2.0 – #43 low Energy, Airtightness, Budgets, & compromise

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 bygge.

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 lifeDisse avgjørelsene var en tightrope spasertur mellom de konkurrerende kravene til å opprettholde vår valgte design, våre krav til lav energibygging og vårt begrensede budsjett.

Noen av våre valg har kommet ned til tilbakebetalingstid. Hvis kostnaden for å gå fra dobbelt til trippelvinduer vil ta, si 15 år å hente gjennom litt lavere oppvarming regninger, så vil du velge det? Hvis det er 30 år i stedet så hva med nå? Poenget der disse tingene gir mening, vil variere for den enkelte. Å si at jeg tror det viktigste kompromisset av hele vårt prosjekt har vært våre vinduer og måtte trene for doble vinduer i stedet for trippel.

Vi vil også ha et Solar PV-system, men det må vente. Det er synd at det er null insentiver i Nord-Irland for varmepumper eller Solar PV etc. Jeg tror vi er den eneste delen av Storbritannia og Irland ikke å ha noen. Muligens vil den nye energiteknikken for NI som kommer senere i år, forandre det.

Som disse bygningsmetodene og produktene blir mye mer vanlige her, vil forhåpentligvis prisene falle. Hvis vi begynte igjen om morgenen, er jeg ganske sikker på at vi ville gå enda enda mer mot passiv standard enn vi har gjort.

Etter å ha bodd i huset i mye mer enn et år nå, er vi veldig glade for at vår beslutning om ikke å brenne noe var den beste.

Lav energi?

[Oppdatering – Her er tallene for våre første års løpekostnad]

Lav energi? Øko hus? Disse vilkårene er ikke godt definert. Men vi har et hjem som i det minste er veldig godt isolert, dra nytte av Solar Acquire om vinteren, bruker et intelligent bygningsstyringssystem, kjører bare på strøm, har en god termisk masse og til slutt stor komfort og luftkvalitet nivåer hele året.

Neste gang

Neste gang ser vi på noen av den nye teknologien i det automatiserte hjemmet. I mellomtiden Husk å sjekke ut vårt instagram for å følge prosjektet, les resten av de automatiserte hjemmet 2.0-bloggmeldingene og finn linkene til alle produktene vi har brukt i vår selvbygging.

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