I decided early-on that I wanted to insulate the boiler in my Elektra T1 for power consumption reasons, and after accomplishing the task, I think I may have rushed into it somewhat. The consensus here seemed to be that ceramic blankets were the way to go, but now I am not so sure. Granted, the ceramic may achieve what your goal is, give or take somewhat, but after looking closer, it looks to me like melamine foam is the most effective (and most cost-effective) way to accomplish the task. Not to mention the fact that I did not really care for all the dust and mess associated with the ceramic blanket (I used the 1/2" Kaowool brand alumina ceramic blanket listed in the photo below supplied by McMaster Carr).
revised 3/15/2008 to add Melamine Foam info
So, unless my calculations are off, the fiberglass would be the choice, with comments:
1. 1" thickness fiberglass blanket is pushing the limits of workability and 1/2" is harder to procure. It may be necessary to compress the blanket more than you would like, reducing it's efficiency somewhat.
2. The K-factor for fiberglass (which is irrespective of the thickness used) or melamine foam is significantly better than ceramic or silicone in general.
3. The R-value for the examples given (which is respective of thickness) is significantly better for fiberglass and melamine foam.
4. The cost per square foot is significantly better for fiberglass and melamine foam, granted the sizes you may be forced to buy for each will vary.
5. Fiberglass or Ceramic either are relatively messy to work with compared to the silicone or melamine foam options.
The most attractive installation would likely be silicone or urethane foam rubber if done properly. However, the cost effectiveness for silicone was the worst of all three options, and without consideration to cost was still inferior to fiberglass. In any event, I have already done mine with ceramic and am mostly pleased with the results, considering it is nice to still have some cup warming ability along with much less heat-on time. However, if I did it again (and I just might if free time allows), I would likely use the melamine foam. The point here was just to share the research with folks who may be contemplating this modification.
Here is a picture of the results (it is encased in copper mesh just to keep it a bit tidier):
Cheers,
Brad
edited 3/15/2008 to add melamine foam info