We use our conservatory year round. It has a glazed roof and one double radiator. It does get warm in summer, but it doesn't have an outside door at the moment, just windows, so I think once it does have a door (this summer) it will be cooler in the summer.
Extension, definitely. We moved into our house 6 months ago - conservatory has 2 sides dwarf walls, 2 sides full (internal) walls, polycarbonate roof.
We love the extra space, but it takes a massive radiator to heat it in winter (to a barely acceptable temperature), and as others have said, it really does suck the heat out of the rest of the house. In summer it was way too hot, even with good roof blinds.
We're now planning to knock it down and replace with a proper extension ASAP.
I love ours for the extra space. We've just moved in and I had two big rads put in before we moved in. Despite this it is still cold, though usable and I second pp who said they could feel the heat being sucked out of the rest of the house. We will put a new insulated roof on (roof revive style or guardian style) as soon as we can afford it. We haven't been through summer, but I expect it will be too hot as it is south facing. Definitely do an extension. Having said that, I do love all the light in the room - it is lovely to sit in on a sunny winter day!
Ours has one full wall and two dwarf walls and we kept the French doors into the kitchen so we could shut it off if we wanted. Ours is north east facing so no heat problem in summer. It has a large radiator and in winter is useable with heating on all the time but with the doors open you can literally feel it sucking the heat from the house. If I had known what it would be like when we added it I would definitely have paid the extra to extend. Difference 10 yrs ago was about 10k iirc.
On the other hand, we put a conservatory on the back of our house with 1 solid wall and 2 dwarf walls, and opened out our kitchen/dining room so now have a large L shaped room at the back of the house. Good insulation, plus a good radiator means we use it all year round.
Oh for any salesman who told you it's a all year round room. Yes it could be if you fancy burning £££ for heating. Got family in the midlands who turn on 3 electric heaters to use their conservatory during winters.
Extension. Same as lavender I found the conservatory freezing in winter and very hot in summer. We have those fancy new pilkington blue glass on the roof and it's still freezing. In summer it's routinely over 30C. But luckily DH and I are from NZ so we have no problem with that, but our british friends couldn't stand that temperature.
The only thing good about a conservatory is hanging laundry. They recommend you to have a separate isolated area to hang wet laundry and the conservatory is perfect for that. (That's sarcasm for that useless room).
I wouldn't never spent money on building a glass room, but it came with our house.
Extension any day. We have a conservatory and its bloody freezing even with the heating on full blast. It's a few years old mind so I'm sure you can get better glazed ones now but I will never have one again and when we can afford it, will knock it down and build a proper extension with an insulated roof.
We have a patio area with walls of our house on two sides (lounge and dining room) and we want to turn it into a room. We first thought we would go for a decent conservatory with dwarf walls on the two sides that will need walls, but now I'm thinking maybe a proper extension would be better, although I guess more expensive.
Wondered if anyone had any thoughts or experience on this?