Cold in winter.....hot in summer. That is a conservatory.!! I had one on my house when I moved in. After two years, realised it was only in use a limited ammount of time due to extreems of temperature. Have now demolished it and built a proper extension onto the house, one side proper cavity wall, with required insulation, other two sides are floor to ceiling glass doors. Underfloor heating as well, (on a well insulated fllor). the roof is a proper pitched tiled roof, very well insulated agian, and with 3 velux roof windows. Now even in winter its warm, with a lovely view out, (also took out existing lounge wall and made living/lounge area twice as big). In summer with some vertical blinds to give a fair bit of shade, as well as roof windows open, allowing heat to escape, the room is fantastic. Moral is that conservatorys by there nature will be very hard to keep at a reasonable temperatue.