I recently asked the #Passivhaus Twitterati their views on how I could explain to my architecture students at IT Sligo what Passivhaus means in ‘real terms’

The response was incredible and I thank (and reference the contributors below):

So the question was; how do you explain in real terms what the Passivhaus Space heating demand of ≤ 15 kWh/(m²a) per annum actually means. (I’ve keeping it simple so leaving out Heating Load for time being). So here we go…

1. The Hairdryer anology

A hairdryer is 1500W

If you have 10 hairdyers left on for 1 hour = 15 kWh/(m²a) (1500W x 10 = 15 KWh).

This would power 1m2 for an entire year.

If you therefore have a house with Treated Floor Area (TFA) of 100m2, and multiply up the hairdryers to 1000 (10 hairdryers x 100m2 = 1000 hairdryers) you have enough power to heat an entire house for the year if you turned them all on for an hour!

This sounds too scary! Next example…

2. The tea-light candle example

One tea candle can produce around 30 watts of heat.

If you have 1 candle lit for 1 hour = 0.3 kWh/(m²a)

50 candles lit for 1 hour= 15 kWh/(m²a) (50 candles x 0.3 kWh/(m²a)

Therefore for a 100m2 TFA house you would need 500 candles lit for an hour to heat the entire house for a year.

Again too scary.

I also found THIS POST on why you shouldn’t be using tea-lights to heat your house & obviously there are health hazards of particulates, ventilation etc!!!

3. The ‘car fill’ example

I like this one:

15kWh/ sq m per year means if you fill your tank with 150 litres (about two fill ups in a petrol station or 1500 km of driving) you will heat a 100 sq m house to toasty comfort for a whole year

I’m going to have to return to this & concentrate instead on heat load!