A temperature monitoring recording session through the cold months can tell you if you have an issue, if i understand the problem it is an enclosed space. That being the case it might not get below 40 in there run a study before you spend more time/money.
Taha;
The answer in most cases in the US is nobody has the answer. There are places where a 26 PSI residual pressure is sufficient for use, if the flow is sufficient to boost.
A static pressure of 26 PSI is a very poor situation.
If you had very large water mains 26 PSI residual pressure may...
http://www.isomitigation.com/downloads/ppc3001.pdf here is a link to how to determine needed fire flows, this will tell you how very deficient the water supply is in the area.
