Temperature, humidity, rain and sun

WHAT IS THE EFFECT OF TEMPERATURE, HUMIDITY, RAIN, AND SUN ON YOUR WOODEN HOUSE  

FOR THOSE WHO WANT TO KNOW IN DETAIL ABOUT THE EFFECT OF TEMPERATURE AND HUMIDITY ON WOOD 

Wooden houses to be built in arid countries
Building in countries with high humidity
Rain and sun 
Building in countries with sub-zero temperatures 
Wetness

WOODEN HOUSES TO BE BUILT IN ARID COUNTRIES

Building your wooden prefab house in an arid area needs very special attention.

A. CLIMATIC CONDITIONS

In the hot and dry zones (arid zones) the most significant problems are those caused by solar radiation and UV rays etc. These can destroy surface finishes, above all coated surfaces of metal sections, metal sheeting, plastic panels, and wood surfaces. In hot arid zones, in which diurnal and annual temperature variations are large, walls should absorb heat during the 9 - 12 hours of solar radiation and then emit the heat to the interior until the cold pre-dawn hours, thus maintaining thermal comfort inside the building at all times (time-lag design theory). Small openings, located at higher levels should permit hot air to escape, and exclude solar radiation and glare.

In hot climates, the long axes of buildings should preferably be orientated in an East-West direction, with openings in the walls facing east and west being avoided or kept small, as it is difficult to shade them from the low morning and evening sun. Openings in walls facing South and North are easy to shade from the high noon sun employing wide roof overhangs.

While the East-West orientation of buildings is important, in hot regions priority must be given to orientation for air movement; in hot arid zones, importance must be given to the exclusion of hot air, sand, and dust.

B. SOLID WALLS

Solid walls with high thermal capacities are common in hot arid climates, as they transfer the absorbed heat to the interior with a time lag, thus restraining the heat when external temperatures are high, and releasing it when temperatures are low. Typical solid walls are made of stone, earth, burnt clay bricks, and concrete. Insulation on the outside of a solid wall gives a four times greater time lag than if it were placed on the inside, but it also hinders heat dissipation during the night. A disadvantage of solid wooden walls is their vulnerability to cracking, even when properly kiln-dried, mainly due to their mass. We advise that solid wooden walls in arid areas be kiln-dried to at least 7% to 8% moisture content (MC). If such is not possible due to the capacity of the kiln a higher moisture content can be applied,  however, one needs to take into account that the wood will take its time to dry out to the lowest Equilibrium Moisture Content (EMC) in an arid country and will cause the wood to shrink based on the difference between the EMC and the MC of the wood when installed. Shrinkages of 3 to 6 mm have been reported. The tongue and groove connections of our exterior siding boards are designed such that these shrinkages can be taken up easily without damaging the wood.

C. CAVITY WALLS

Double-walled construction has many advantages, both in warm humid, and hot arid regions such as:

• The outer layer protects the inner layer from direct solar radiation, which first heats the outer layer. With a reflective outer surface, this heat absorption is greatly reduced;
• Only a part of the heat that passes through the outer layers reaches the inner layer by radiation or convection, and if provided with a reflective surface, it will not absorb all the heat;
• The insulation materials used for cavity walls can be of various types, depending on several factors, such as temperature range, intensity and duration of solar radiation, humidity, building usage, and nature of immediate surroundings, and can be insulated with either glass wool, rock wool or polystyrene foam boards will double act as an insulator, which is an advantage opening at the top and bottom of the cavities allow the hot air, which will have accumulated within, to escape at the top, while fresh air is drawn in at the lower side. During the day, when the fresh air is also hot, air circulation will have no cooling effect, so it would be ideal (but not practical) to be able to close the openings during the day and open them at night;
• Sound transmission is reduced by the air space.
• In warm humid and dry climates, double-walled constructions have the additional advantage of protecting the inner layer from rain and moisture penetration. Any moisture that passes through the outer layer is removed by ventilation, and condensation water can trickle down and out through the opening below.
• In warm humid conditions, the inner skin should not be impermeable, as moisture movement is required, while the outer skin (usually thin panels or tiles on lathing) can be either impermeable or not, but care must be taken to avoid moisture bridging from the outer to the inner skin.

The maximum moisture content of double wooden walls in arid areas shall be around 5% for exterior walls and 10% for interior walls, flooring, beams, and columns

D. ROOFS

Roofs are always in the first line of attack by sunlight and easily and fast heat up and are one of the most crucial building elements whereas it is a source of considerable radiant heat. The roofing system, which may include a plenum concept, needs to be designed to be self-ventilating or cooling and to be constructed of materials that have a higher thermal value. 

Our company would be happy to advise and recommend the type of building materials and the way of building your tropical wooden prefab home in an environment.

BUILDING IN COUNTRIES WITH HIGH HUMIDITY

Wood is a hygroscopic material—meaning that it will gain or lose moisture until it reaches an equilibrium with its surroundings. If the surroundings are hot and dry, then wood won’t be able to hold moisture for long. If the air is cold and wet, then the wood will start absorbing some of the excess moisture in the air. It is important to measure moisture in the flooring wood as well as the ambient temperature and humidity conditions before installing hardwood floors. The fastest way to measure moisture in boards is to use a moisture meter for wood. These devices can be used to test the moisture content (%MC) of wood flooring in mere seconds. On the right, a picture of our moisture meter is shown.

Most wooden boards will expand and contract along the width of the board with typically little expansion or contraction lengthwise or along the thickness of the board. The moisture content standard of our boards is 12% and 15% with a 2% tolerance (the moisture content of 12% to 15 % is the maximum we can achieve in Bali with the currently available kilns on the island. The moisture content is carefully controlled throughout the kiln process and it leaves our factory within the tolerances. However, once the flooring is put on the truck for delivery to our assembly yard it is subjected to a host of various conditions that may adversely affect the moisture content. Hardwood boards need to be properly acclimated to the environment in which it is installed. The sidings and flooring should be moisture checked by one of our supervisors with a professional moisture meter and the level recorded. The moisture content of all the boards should be no more than the accepted 2% tolerance.  

In conclusion: Our wood used for the prefabrication of wooden houses will be 12% to 15% (plus or minus 2%) for boards and not more than 35% for beams and columns

RAIN AND SUN

Two unavoidable factors that will impact wood in an exterior application are rain and sun. They will definitely; have an impact on the natural wood color when exposed to rain and sun. 

Wood that is kept dry and away from sunlight in an indoor application will last indefinitely. But what happens when the wood is frequently exposed to the sun’s rays and moisture from the rain? In simple terms, the surface of the wood starts to break down and decay, whereas the wood begins to split, rot and decay,

That is why exterior wood shall always be treated with a proper coating. Before the transport to the destination, all of our wood will be coated with several layers of acrylic, which will give full protection for at least 5 years, whereafter a new coat needs to be applied. 

BUILDING IN COUNTRIES WITH SUBZERO TEMPERATURES

If you’re going to be building a timber home in an area that’s subject to freezing temperatures and seasonal changes, planning before building is important. This is true regardless of the materials you’ll be using.

Here are some key considerations:

Location and Orientation – If you can, choose a south-facing orientation for your timber frame home, to maximize the benefits of winter sunlight.
Foundation Depth – For a timber frame building in a cold location, such as a northern U.S. state, foundation footings must be below the maximum frost depth.
Built-Up Roof System – This roofing system provides a vented air space (the furring strips system) above the insulation to minimize moisture buildup and deliver superior fire and uplift performance. It also protects the roof from extreme weather, UV, and ice dams. 
Insulation – A proper insulation system delivers high energy efficiency and thermal value. They create a strong building envelope that seals the interior living environment from the outside, saving homeowners as much as 50% of heating and cooling costs compared to fiberglass insulation.

Keep in mind the adage "It's not the heat, but the humidity" when considering wood movement. Most properly dried lumber won't have enough moisture content for its dimensions to be affected by freezing temperatures. Winter weather often brings drastic drops in humidity and thus will affect wood if not properly kiln-dried. It will crack and deform. Refer to XXXX for our kiln drying system. 

WETNESS 

Most species of wood don't do well when exposed to rain with some exceptions, like Bangklirai, Merbau, and Teak. Nonetheless, they need the protection of a finish to protect them from rain and humidity, or else they quickly warp, crack, and rot.

When wood is part of a tree, its cells are full of water. When the tree is cut and the wood milled, the cells slowly dry out and shrink. Exposed to rain, the cells reabsorb water and swell, and they shrink again when the sun comes out. This natural movement can cause gaps or curling when boards are installed next to each other. It can also cause cracking and warping, depending on how evenly the cells shrink and swell.

Rain causes rot in wood that lacks the natural oils to resist it by creating the moisture necessary for microorganisms to flourish. Exterior wood in shady locations is most vulnerable, as are joints between boards in which water collects. Even weather-resistant species may become vulnerable in extremely wet, shady conditions. The best way to avoid rot on exterior wood is to paint or finish it regularly. In conclusion: A proper coating system and regular maintenance (refer to our maintenance schedule in the warranty certificate) will protect the wood from rotting and early deterioration. 

  Properly coated against rain and sun