Radiantec Logo
Sunset over Solar Panels

printer friendly version

Call Toll Free 1(800)451-7593

Get your Free Quote Today!

Solar Power Your Radiant System

Find us on Facebook
free quote here

Closed System

This system uses a high efficiency water heater or boiler and the heating fluid is self contained within the system and stays there unless removed for maintenance. The heater warms the water or another fluid such as anti-freeze. When heat is called for by the thermostat, a pump comes on and circulates the warm water throughout the floor until the thermostat is satisfied.

Animation illustrating the functionality of a closed heating system.

Legend for Closed Direct Heating System animation


  1. Very well accepted by code officials because the domestic hot water is completely separate.
  2. Easy to have a combination of high temperature applications such as baseboard and low temperature applications such as radiant.
  3. Mechanically very simple.
  4. Anti-freeze can be used if desired.
  5. Having redundant systems can be beneficial; if your heat fails, you still have hot water for showering and vice versa.


  1. Slightly more expensive than the Open Direct System because you need a separate water heater for domestic purposes.
  2. Free cooling benefit is eliminated
  3. Oxygen barrier tubing is often required if a boiler is used.
  4. The system may not be quite as efficient if a boiler is used. See water heater vs. boiler

Click here to get a quote on this system!

Closed System Example


About Radiantec
Radiantec Qualifications
Customer Support
A+ BBB Rating
Quote Cover Letter
Take the Next Step
Request a Brochure
Quick Quote Form
Full Quote Form
Customer Testimonials
Installation Packages
Installation Manuals
About our Products
Freq Asked Questions
Why Radiant Heat
Technical Description
Environmental Benefits
Radiant Heat for Log Homes
Retrofit your Home
Solar Power Your System
Radiantec R & D
The Best Overall System
Engineered Tubing Benefits
Insulation and Heat Migration
Study of Heat Transfer Plates
US DOE Report
ASES paper
Our Heating Systems
The Best Overall System
Radiant Heating Systems
Closed System
Indirect System
Open Direct System
Water Heater heat source
Going Solar - Free Energy!
Cost Saving Benefits
Environmental Benefits

Installation Manuals

About Building Codes
Problems w/a code official?
Shop Online
About our Selection
Pricing Information
Do It Yourself
Installation Packages
Individual Component Prices
Ballpark Estimates
Sample Project Cost
Quick Quote Form
Full Quote Form
Tax Credits are Possible
ICC ES Evaluation Report
Installation Manuals
Design & Construction Manual
Open Direct System
Installing the Closed System
Installing the Indirect System
Installing tubing for a concrete slab
Installing tubing between floor joists
Installing tubing in the ceiling
Installing tubing in the walls
Installing a heated towel rack
Installing Radiantec Controls
Doing your own tubing layout.
Radiantec Basic Solar Domestic
   Water Heater Installation Manual.

Radiantec Basic Solar Domestic
   Water Heater Owners Manual.

tubing background