How to heat and cool a new addition or sunroom on Long Island — ranked by cost, comfort, and ease of install.
One of the most overlooked parts of a home addition is how you'll heat and cool it. Extending your existing ductwork isn't always possible — or smart. Here are the best options for keeping a new addition comfortable year-round.
We build the addition and handle the HVAC, so we plan this from day one — not as an afterthought.
A ductless mini-split is the ideal solution for most additions — no ductwork required, independent zone control, fast install, and excellent efficiency for both heating and cooling. As authorized Mr. Cool installers, this is what we recommend most.
$3,000–$8,000+ per zone
If your current furnace/AC has spare capacity and ducts can reach the addition, extending the system keeps everything on one thermostat. The catch: many existing systems are already maxed out, which leads to uneven comfort.
$2,000–$6,000+ depending on runs
A dedicated heat pump efficiently heats and cools the new space and can qualify for rebates. Great for larger additions where a single mini-split head isn't enough.
$5,000–$12,000+
Simple and inexpensive to install for a small bump-out or sunroom, but operating costs run higher and it only heats. Often paired with a window or portable AC for summer.
$1,000–$4,000+
For nearly every Long Island addition, a Mr. Cool ductless mini-split is the best choice — it heats and cools, installs cleanly without tearing into the rest of the house, and gives the new room its own comfort zone. We design the addition and the HVAC together so the space is comfortable from the first day you use it.
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Sometimes — but only if your current system has spare capacity and the ducts can reach. Many existing systems are already sized for the original house, so adding more space leads to weak airflow. A mini-split avoids that problem entirely.
A ductless mini-split is the cleanest, most efficient way to make a sunroom usable year-round — it provides both heat and AC with a small, quiet indoor unit and no ductwork.
Yes. Modern heat-pump mini-splits are designed to heat efficiently well below freezing, which easily covers Long Island's winters.
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