Planning a system change: Forewarned is forearmed....

[dbheat]

Hello! My first post.
Am trying to plan for a DHW and CH system change for my mam, who gets plagued with cold calls from grant/boiler people. System overdue a change, but winter bad time to do it in many ways. Grants people may be useful, but only if I know what is what. I am wary of them. The most complex system in a house, by far, is the heating and hot water. She (I) need to plan ahead. I would be grateful for any input from you guys.
As an aside, why ask here you say? Well three very local heating guys were asked to quote for a radiator addition, two turned up, no quotes received. No reason why given. The two trade guys I know and trust.. one is a general plumber and the other is dead.... If I start talking with some bloke with sums of money in the k's, even if I should chance on a good bloke, I need to know the basics.

So: Combi v ordinary boiler or alternatives? Then of course, size?
Zone heating or room stat and TRV? The upstairs need to be warm, and for longer periods of the day than downstairs.
10mm/15mm?
Will post sizes and current system later

 

[dbheat]

7m x 7m detached. 3 beds & bath, 1 downstairs & kitchen. 50ishmm loft insulation, blown eps cavity wall insulation (or whatever is left in there after the windows were changed!) Double glazed 17msq all in. No Conservatory.
Current system:
Boiler Thorn Olympic 20b (5.86-10.26kw) Annually serviced. elson diamond indirect hot water tank 135l no other system components.
Gravity hot water and heating, 8mm microbore to total about 8kw of rads (calculations difficult because non-convector) total about 1.9sqm double panelled and 2.1sqm single panelled.

 

[GavThePlumber]

How many occupants, what is hot water consumption like? You spec boilers for hot water demand, not heating.

 

[kbdiy]

... and if she only has 50mm loft insulation she needs a LOT more. It should be 270mm minimum to meet current standards.

 

[dbheat]

1 occupant always. Two at most. General average useage.

 

[dbheat]

Thanks for the reply kbdiy. I know! Loft space is used for storage and is floored. Did not fancy the job this summer(!) and it will be wip soon

 

[GavThePlumber]

Install a combi boiler and get rid of the hot tank and cisterns in loft and install TRVs on all but one rad (where the stat is)