Size matters… BUT SO DOES CLIMATE. Building a house for a hot or cold climate— BYHYU 015

Martin Holliday of the Green Building Advisor website says “If you go to one of the many web sites that sell house plans, you can use filtering software to sort through hundreds of available plans by a variety of criteria: square feet, number of bedrooms, number of bathrooms, number of stories, or even number of garage bays. On most of these sites, however, you can’t sort by climate zone. Why? Because most house plan companies ignore climate. They’re happy to sell customers in Minnesota the same house plan that they sell customers in Florida.” 

​That’s why today’s mini lesson covers some different design features and construction practices that are suited for either a cold or a hot climate. My goal is for us to get a general background about the differences in building a home in these different climates. We don’t have to know ever detail about regional climate design, but  I want us to learn enough to make educated decisions about  our construction choices.  And learn enough so we can ask about some cutting edge and common sense options that maybe our contractors might not typically offer.

Before we get into the lesson, let’s go over our Pro Term: 

Furring

In construction, furring (sometimes called wall furring or furring strips) are thin strips of wood or metal or other material that are fastened to a wall or other surface.  Exterior siding or wall panels can be attached to furring strips. Furring is used for several reasons 1) to make an uneven surface level, 2)  to form an air space between one surface and another to prevent dampness 3) to make space for insulation or 4) to make the wall look thicker.  

You'll see the word "furring" in our mini lesson.  Let's get to it.

A home’s design and construction should take into consideration the region’s typical maximum and minimum temperatures and the amount of wind, snow, sunlight and rain that the area gets.  In hot areas you have to guard against the discomfort of too much sunlight and heat and in a cold climates, you have to guard against bursting pipes,  chilly rooms, and icy driveways.  Let’s go over some differences that you should see in hot climate versus cold climate design.


Foundations can vary significantly in a cold vs hot climate. Footings of most foundations must be placed below the frost line.  The frost line is the depth at which frost or ice penetrate the ground.  Ground above the frost line freezes and ground below the frost line does NOT freeze.

In cold climates most homes have foundations that begin several feet below grade, meaning below ground.  So since they have to  dig that far below ground anyway, many people in cold climates decide to utilize that space and put in basement foundations.

In hot climates, the frost line may be only a few inches below grade, or there may not be a frost line at all.  So, a slab foundation is often used in hot climates.  In hot climates, those slab foundations should not have horizontal insulation under a slab.   Here’s why:   Without horizontal insulation, the slab is in contact with the cool soil and that cool soil  can help keep the house cooler and lower a homeowner's utility bills. In colder climates, however, horizontal insulation under a slab on grade is a must because you don’t want the cold soil cooling the house
down. If you are curious about the frost line is in your area of the US, I’ve included a frost depth map below.




 
Lastly, let me give you a tidbit about foundations for rainy climates.  In rainy climates, if a wood framed home is close to the ground, it is more prone to rot because of excess water.  But you can decrease your risk of rot if you leave 10 or 12 inches of the concrete foundation exposed above grade.  That way you have a greater distance between the wood framing and the water near the ground.  


Windows:  Windows can be a challenge because they allow the sun’s heat to enter the interior of the home in hot climates and they allow the home’s heat to escape from the house in cold areas. If your climate is cold and cloudy, unless you have a view, you probably want to minimize large, expansive windows, especially on the north side of the home. 

In a hot, sunny climate, north and south facing windows shouldn’t cause any significant problems, but you definitely want to minimize the your east-facing and west-facing windows since these windows are difficult to shade.  Hot climate windows should also be recessed into thick walls, if possible, for greater sun protection.


Selecting the best window for your home is a complicated topic best left to its own episode. But choosing the most energy efficient windows that will fit into your budget is important in cold and hot climates.  As a rule of thumb, know that cold climate windows should have a higher solar heat-gain coefficient and windows in hot climates should have a lower solar heat gain coefficient.  Makes sense, right?


Roofing:  A simple roof design, like a gable roof, sheds snow and ice more easily than a complicated roof designs. A gable roof your typical neighborhood roof that has two sloping sides that come down to make a triangle. In cold regions with heavy snowfall, your roof should have a steeper pitch since a steep pitch sheds snow better than a roof with with a shallow pitch.

And you should minimize the roof openings such as skylights and chimneys in cold climates.  Those openings can encourage the accumulation of hard to melt ice and snow which could result in a roof leaks.  A metal roof is the most durable and rarely springs a leak.  It also shed snow well.  But if you want a slightly less durable, but more affordable option, choose a good quality asphalt roof.  


In a cold, snowy climate, a house designer has to anticipate where snow will land when it slides off a roof. This is especially important for roofs on garages and near entrances, so you aren’t blocked in when snow slides onto the ground.  When looking over your house design make sure there is plenty of space on the ground below the roofline for shedding show.  

Another option is to have snow guards installed.  Snow guards are rooftop devices that allow snow and ice to drop off in small amounts or to melt completely before falling to the ground. The installation of snow guards prevents the sudden release of snow and ice from a roof. 


In hot climates, the roof overhangs are important. Houses benefit greatly from large overhangs which provide shade.  Specifically, consider a hipped roof where the roof starts from a center, top peak and all sides of the roof slope downward to form relatively wide roof overhangs. These overhangs will keep the sun off the windows on all sides of the house. Some experts recommend overhangs of 3 feet or more.  And remember to ask for hurricane clips for roofs with large overhangs, if you are in a windy or storm prone area since high winds can more easily grab a roof with large overhangs. 

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gable roof

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hipped roof

Roof overhangs are also important in rainy climates to decrease the amount of the rain, and resulting rot, that can affect the sides of the house. Soffit vents are also typically installed in rainy climates to increase ventilation and decrease chances of rot. 

Pop Quiz:  Soffit was a pro term in last week’s episode.  What is a soffit? 
A soffit is the sidewalk or downward facing part of the roof’s edge or eave. 

In cold climates choosing darkly colored roofing is beneficial because it will attract the sun to help melt snow. In hot climates, on the other hand, you might want to go with a light-colored roof or a so-called “cool roof” that has been designed to reflect more sunlight and absorb less heat than a standard roof.


Driveways: In cold climates. although they are expensive, you can have snow melting systems installed beneath driveways and frequently used pathways.  Whether you use a snow melting system or not, be sure that driveways and walking paths are covered by hard, level surfaces like poured concrete or pavers instead of gravel.  Gravel paths are difficult to impossible to shovel well.


Framing and wall systems:  Since cold climate homes typically have higher energy costs than homes in hot climates, U.S. building codes require that homes in cold climates have more insulation than homes in hot climates. 


Wall insulation is much less crucial in hot climates than in cold climates. No single wall system is considered ideal in any climate–each wall system has its own advantages and disadvantages.  It doesn't really matter what you use as long as the wall assemblies have the R-value your looking for and everything is built and installed correctly. 


The 3 wall systems that most people choose from are 1) Stick or wood framing with added insulation, such as blown-in cellulose, spray foam insulation or foam board insulation 2) ICF (insulated concrete forms) walls, which are pretty expensive, but very strong and energy efficient.  ICF’s should definitely be considered if you live in a windy or storm prone area. The third wall system to consider is SIPs. 

Pop Quiz:  Do you remember what SIP stands for and what a SIP is?    It was our pro term in episode 4 called “Do you need a structural engineer? Part 2”.  Well, SIP stands for Structural Insulated Panel and is a core of foam insulation sandwiched between to structural boards, usually oriented strand boards.  SIPs can be used for wall systems or for roofing systems.  


If you’re considering ICFs or SIPs for your wall system,  be sure to compare the cost of those systems with other wall system designs.  Those systems have significantly higher up front costs when compared with stick framing with added insulation.  


In addition, if not installed properly, SIPs can are vulnerable to moisture problems. To decrease the chances of those moisture problems, joints in the panels must be sealed well, according to manufacturer specifications, the home’s roof should be ventilated, plus you should consider furring over the structural insulated panels. 


There aren't just challenges with SIPs.  One of the biggest challenges with  stick framing wall systems is heat loss through the wall studs. Studs between insulated cavities will conduct heat, and that’s not good.  No matter which wall design you settle on, try to avoid this thermal bridging.

Remember a thermal bridge is an area where there is increased (and unwanted) heat transfer.  One of the best ways to prevent thermal bridging is by using continuous insulation, for example wrapping the exterior of an stick framed house with rigid, foam insulation.  Ideally, your home will have a continuous "shell" of insulation that is broken only by windows, doors, plumbing penetrations, and ventilation.


What’s important in both hot and cold climates: 


It’s important to minimize air and duct leakage no matter what your climate is. Tight houses are much easier than leaky houses to keep comfortable.
It’s also important the home’s HVAC systems and all ductwork to be within the home’s thermal envelope and in all climates duct seams should always be carefully sealed.


And since we all want to build fairly tight homes whether we live in Florida or Maine,  mechanical ventilation for get fresh air into and take stale are out of the home is important in all climates.


Whether you live in a hot or cold climate, consider hiring a home energy rater to model your home for greater energy efficiency.   An experienced rater may be able find alternative design approaches in the building shell of your house to improve its thermal performance.  A rater should also be familiar with local climate conditions and building codes.  If you want more information about home energy raters, take a listen to episodes 11 and 12.

QUIZ

1. Furring is used for all of the following reasons except:
 A.  To make an uneven surface level 
 B.  To form an air space between one surface and another to prevent dampness 
 C.  To provide an attractive covering for windows
 D.  To make space for insulation 


Furring is thin strips of wood or metal or other material that are fastened to a wall or other surface for all the above mentioned reasons except C.  It is not a window covering.




2.  True or false:  Gravel driveways and pathways are a good idea for cold climates.



False.  Ultimately the choice is yours, but ice and snow are difficult to remove from gravel driveways, so more level surface such as concrete or pavers would be a better choice.



3. Is a gable roof or a hipped roof better for a hot climate and why?




Again, its ultimately a matter a choice, but a hipped roof is better for a hot climate because it has overhangs on all sides of the house which provide much needed shade in hot climates.



That’s it for this week. I hope you learned as much as I did this week.  If you know anyone who could use some tips on building in a cold or hot climate, you can share this episode with them by text, email, Facebook or Twitter.  Just hit the share icon towards the right of the podcast player.  Look for the 3 small circles within a circle.


Please remember that the purpose of this podcast is simply to educate and inform.  It is not a substitute for professional advice.  The information that you hear is based the only on the opinions, research and experiences of my guests and myself.  That information might be incomplete and it’s subject to change, so it may not apply to your project. Always consult a professional about specific recommendations for your home.