We have been living in our home for a number of years now, so have seen several summers and winters, but we are still looking to solve the heating and cooling problems we have.
The walls and roof of the house are well insulated, and upstairs only has relatively small Velux windows, so upstairs is always warm enough, even in the depths of winter.
The open plan downstairs however is laminate flooring on concrete with minimal under floor insulation, so the floor is always cold, and it's always a struggle to get downstairs to feel warm in winter.
Even when downstairs is warm enough and the upstairs radiators cold, upstairs is almost always too hot, so a huge temperature differential exists.
So far we haven't had many problems with downstairs being too warm in summer, but upstairs can get uncomfortably hot, especially in our bedroom.
Neither of us sleep too well if too hot, so we are currently looking at options for air-conditioning. I am concerned about our environmental footprint however and would prefer a more sustainable solution if possible.
All radiators except the upstairs bathroom towel radiator (which acts as a bypass radiator) are controlled by TRVs. Originally they had thermostatically controlled valves, but switching to smart valves just confirmed what we already knew, the logs show that upstairs radiators never turn on.
Downstairs consists of a small toilet room (2m²/22ft²), plus a large open plan area consisting of living and dining areas, stair well and kitchen which is also open to the conservatory (a total of 39m²/416ft²), where all external doors open into this area.
The central heating is relatively new, so the condensing gas combi-boiler is quite efficient. It has a SEDBUK rating of 90% and a heat output of 24.9kW, which should be more than enough to heat a to heat 77m² / 826ft² house.
In the UK gas is much cheaper for heating than electricity, so we currently pay 8.3p/kWh for gas (at 90% boiler efficiency) and 28p/kWh for electricity (that's 10 & 36 cents/kWh at current exchange rates) so we would prefer the bulk of the heating load to be carried by the gas central heating.
Down the line we would like under floor heating downstairs, but that would be a big, disruptive job, teh same as addadding more radiators. We will also eventually get around to replacing the patio doors and the conservatory, which should help with insulation downstairs, but again those are longer term plans.
How can we equalise the temperature between upstairs and downstairs?
I've already added a vent and duct fan to pump cold air from downstairs to upstairs, but this doesn't help with extracting the hot air from upstairs.
I thought of just fitting an insulated duct and a fan which extracts air from upstairs and pipes it downstairs, but the only place I could fit such a duct would be in the stair well, and it feels like the air would just end up circulating straight back upstairs. Other than that we would need to take a duct outside, which feels like a lot of work for an indeterminate benefit.
We have sought out quotes for a standard split air conditioner unit to cool upstairs, but that won't help with heating downstairs and I'm not happy about the environmental impact.
I was hoping that there may be solutions which could pump heat from upstairs to downstairs, but normal split air conditioner systems can't be configured to take advantage of temperature differentials like this.
Since upstairs is almost always too hot, even in winter, and downstairs is almost always too cold, even in summer, the absolute last thing I want is to be using electricity to cool upstairs all year round, at the same time as we are burning gas to heat downstairs. This would have an unacceptable environmental impact to us.
Note, I'm not looking for product recommendations, or someone to do a complete analysis of our situation, the detail is more to illustrate an example of the more general problem. What I am looking for is what would be considered a sustainable solution to the more generic problem of equalising temperature throughout a house with differing levels of heat load and desired temperatures.