Adding a Sunroom?

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Imagine that it’s 20 degrees outside – but sunny. You’ve just come in from shoveling the driveway, and now you’re sitting comfortably in your sunroom, surrounded by houseplants, sipping some hot cocoa and soaking up the warmth of the sun.

Summer is not the usual season when people start to wish they had a sunroom. These days, you’re out on the porch, deck, or patio. The longing for an indoor sunny spot won’t blossom until late Fall or Midwinter.

Bad timing! Here in Northern New England, the best time to start an addition of any type is in Spring or Summer (and maybe Fall, if you start early enough to get it closed in before the temperatures get too low).

Timing is just one of the issues that you need to consider when planning a sunroom, and a sunny day in Summer is not a bad time to start planning. Why? Because you can get a good idea of how hot a sunroom can be that time of year. A well planned sunroom should be comfortable year round.

Here are important points to consider:

  • Uses (relaxing, chatting, eating, starting the veggie garden . . .)
  • Orientation (generally south, but not necessarily due south)
  • Location of nearby trees (winter sun versus summer shade)
  • Height of the glass (a kneewall can be useful)
  • Roof overhangs (for summer shading)
  • Type of flooring (thermal mass moderates the temperature)
  • Ventilation (all sunrooms need it)
  • Additional heat and cooling (will you need it at all?)

A Sunroom Is Not a Greenhouse

This is an important point. While you may want to use the sunroom to start your vegetable garden plants in the spring, it’s not intended as a dedicated greenhouse. You should not put in a sloped south wall, because the room will get too hot in the summer. Skylights or roof windows are also mixed blessings. While it’s useful to be able to open the roof up for ventilation, you’ll need shades up there to keep out the summer sun.

This is also a good reason for orienting the sunroom away from due South. Generally Southeast is better, because the morning sun helps to warm the room more quickly during the cool seasons, and also provides a morning lift to the spirits. Conversely, the afternoon summer sun can add too much heat just before bedtime.

Knee Walls and Roof Overhangs Are Useful

A full-length glassed door is a wonderful thing to have, but the walls don’t have to be full length. Knee-height walls help to keep the snow from building up against the glass and also provide a low shelf inside. Consider using sliding windows and doors, as well. When all of them are open, half your glass will be out of the way, leaving you with a very close approximation to a screened porch.

Wide roof overhangs are a must. The sun is low enough during the cool seasons that the overhangs won’t block out much light to speak of, but they will do a very good job of shading the room during the Summer. Plan on pull shades, blinds, or drapes as well. They’ll keep heat in during the night and out during the day.

Shade Trees Are a Blessing

Speaking of shade, don’t plant pines or other evergreens where they will shade your sunroom. Instead, calculate where on the horizon the sun rises and sets at Midwinter and plant deciduous trees just outside these sun lines. Maples, oaks, basswoods, honey locusts – there are dozens of species to choose from. They’ll provide shade during the summer but drop their leaves and stay out of the way during the Winter. During the transition seasons of Fall and Spring, they’ll provide partial shade but still leave open sky for most of the day.

Thermal Mass Moderates the Heat

Build the sunroom on a very well insulated slab and finish it with slate or tile. The masonry floor will absorb heat during the day and release it slowly during the night, keeping your feet warmer, and moderating the temperature extremes. The room won’t get as hot at midday or as cold at midnight. Throw rugs in the right spots will soften the floor for your feet without cutting down too much on heat absorption.

Dealing with Heat Gain and Loss

Because the sunroom juts out from the main body of the house and is walled mostly with glass, it will put some additional demands on your heating and cooling systems. Thermal mass, intelligent shading, and good ventilation will help solve those problems, but you’ll need to consider some auxiliary heating at least.

The sunroom will heat itself when the conditions are right, so a direct connection to your existing heating system may not be necessary. You can use space heaters on the cloudy days and perhaps a quiet fan to circulate heat in through a vent or open doorway. If the fan is reversible, you can also blow heat into the house on sunny days. Open windows combined with a circulating fan can help cool the rest of the house on hot summer days (assuming you don’t use air conditioning).

Done right, the sunroom might even cut your heating and cooling bills! But remember, you need to start building it by Fall.

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