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 costruire.
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 life, queste decisioni sono state un cammino della corda tra le esigenze concorrenti di mantenere il nostro design scelto, i nostri requisiti per una build di energia bassa e il nostro budget limitato.
Alcune delle nostre scelte sono scese al tempo di pagamento. Se il costo di andare dal doppio alle finestre vetrate a triplo prenderanno, dicono 15 anni per recuperare attraverso le bollette di riscaldamento leggermente inferiori, allora optiamo per questo? Se sono invece di 30 anni, allora che ne dici? Il punto in cui queste cose hanno senso varieranno per l’individuo. Dicendo che, penso che il compromesso più significativo del nostro intero progetto sia stato le nostre finestre e dover funzionare per doppi vetri invece di triplo.
Vogliamo anche un sistema PV solare, ma ciò dovrà aspettare. È un peccato che ci siano zero incentivi nell’Irlanda del Nord per pompe di calore o Solar PV, ecc. Penso che siamo l’unica parte del Regno Unito e dell’Irlanda di non avere nessuno. Forse la nuova tecnica energetica per NI che arriverà più tardi quest’anno cambierà questo.
Poiché questi metodi e prodotti di costruzione diventano molto più comuni qui spero che i prezzi cadranno. Se stavamo ricominciando la mattina, sono abbastanza sicuro che saremmo andati ancora di più verso lo standard passivo di quanto abbiamo fatto.
Dopo aver vissuto in casa per molto più di un anno ora siamo molto lieti che la nostra decisione di non bruciare nulla fosse la migliore.
Bassa energia?
[Aggiornamento – Ecco le figure per i nostri primi anni in esecuzione]
Bassa energia? Eco House? Questi termini non sono ben definiti. Ma abbiamo una casa che, per lo meno, è davvero ben isolata, sfrutta l’acquisizione solare in inverno, utilizza un sistema intelligente di gestione dell’edificio, funziona solo sull’elettricità, ha una buona massa termica e alla fine grande comfort e qualità dell’aria Livelli tutto l’anno.
La prossima volta
La prossima volta esamineremo parte della nuova tecnologia nella casa automatizzata. Nel frattempo ricorda di controllare il nostro Instagram per seguire il progetto, leggere il resto dei messaggi automatici del blog Home 2.0 e trova i collegamenti a tutti i prodotti che abbiamo usato nella nostra auto-build.
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