Why get a proper radiant design? Why get a proper radiant installation?
It is not hard to find an existing hydronic radiant heat system that does not work the way it should.
Typical problems are:
Inadequate heat
Inadequate Domestic Hot Water
Grossly oversized and inefficient boilers.
Wrong Temperature to radiators, baseboards, under floor or in slab
Condensing boiler problems
Conventional boiler problems
non o2 barrier pipe
Hardwood floor problems
etc.
It simply is not worth risking an expensive installation without a proper design. If your installer will not give you a copy of their design including floor loops, they likely don't have a proper design, and likely install on the fly at your jobsite.
Examples of common problems without proper design
Inadequate heat
Typical Scenario 1
Super best plumbing company sends out their new apprentice with instructions to install pipe at 1 ft spacing in a room that is 400 square ft. Tube lengths not to exceed 300 ft.
Apprentice starts laying tube, runs to 300 ft then starts next loop, next loop is only 100 ft.
(Now needs proper balancing to get water to flow through 300 ft pipe.)
Or Typical Scenario 2
Apprentice starts laying tube, runs to 300 ft. Apprentice sees that there is only a small area of room left, so decides to just finish off room with one loop of 400ft. to save time and money. (circulator may not be able to adequately overcome the added resistance (ft of head).
Proper design in these typical scenarios' actually shows 1 ft spacing will not provide enough heat. Design has 6 inch spacing along colder outside wall with 1 ft spacing in balance of room and has 2 equal lengths of 250 ft.
Typical Scenario 3
Super best plumbing company sends out their new apprentice with instructions to install pipe at 1 ft spacing in an ensuite that is 150 square ft.
Apprentice lays his typical 1 ft spacing and loop works out to 100 ft. He does not run tube under bathtub or cabinets.
Ensuite installations typically have lots of windows and limited floor area.
Proper design shows that 1 ft spacing did not provide enough heat; even 6 inch spacing did not provide enough heat. Design has 6 inch spacing under exterior walls and cabinets, under bathtub and still needs additional heat. This can be provided with towel warmer, in the wall radiant heat, kick space heater or radiator.
Inadequate heat can also be caused by kinked lines, boiler too small, improper loop temperature etc.
Inadequate Domestic Hot Water
Super Best Plumbing Company installs a 45,000 BTU boiler just like all their other installs in a similar house. They then connect an indirect domestic hot water tank to this boiler.
Proper Design calculates additional BTU requirements for indirect DHW tank of 25,000 BTU, so proper Boiler size works out to 70,000 BTU
Grossly oversized and inefficient boilers.
Super Best Plumbing Company often installs very large boilers just to be safe, without doing proper heat loss calculations.
Many Older installations have grossly oversized boilers. One example is this oil fired boiler at 160,000 Btu which nets probably 100,000 Btu. This boiler is twice the size it needs to be. So it is like a 1970's Cadillac Eldorado with a 500 cubic inch V8 engine that gets 11.3 miles per imperial gallon. When this large boiler fires it very quickly gets the water to temperature then quickly shuts down. It is short cycling and not running efficient.
Heat loss will determine proper boiler size, just like reccomending a modern small car with very good miles per gallon.
