SIP Construction for Costa Rica
SIP panels or Structural Insulated Panels are lightweight but strong panels used for walls, floors and roofing. They usually consist of a lightweight Styrofoam core sandwiched between two sides of Fiber cement or Magnesium Oxide boards (MGO). SIPs are manufactured under factory controlled conditions and can be fabricated to fit any building design.
Main Advantages of SIP construction
- Various Cost advantages
- Extremely strong
- High Insulation and R-Value
- Environmentally responsible building system
- Fire Resistant
- Protect from mould growth and insect infestation
- Modular panel system for Prefabrication
In Costa Rica and its humid hot climate with lots of earthquakes a lightweight and strong building material with high insulation value is a great alternative to locally used methods and materials like Cinder Blocks. It can be proven that a SIP panel house is actually cheaper in total construction cost than a conventionally built one due to material and labour savings. In the long run other substantial costs savings can be achieved due to the high insulation value when used for air conditioned homes. Those energy savings make SIPs a green building material which save money and electricity. Further advantages are that SIP construction panels can be prefabricated in a controlled shop environment and plumbing and electric can be prewired and installed which cuts down on site work and labour.
SIP Construction compared to Block Construction
Costa Rican builders but also a lot of US builders working in Costa Rica still go with the conventional methods of building which is mainly Cinder block or Concrete panels for low end homes. Both systems are used mainly because costa rican workers and engineers use them for years so they keep using them. But compared to SIP panels there are only disadvantages if you compare them side to side.
A concrete or cinder Block wall or floor system is about 18 heavier than SIPs. The specific weight of concrete is 2500 kg/m3 compared to 135 kg/m3 for SIPs so by a factor of roughly 18. In an earthquake the higher mass has to be reinforced much more than a lightweight building. This then leads to even higher total weight and costs due to massive oversizing of beams and foundations.
SIPs also have about 15 times the insulation value since concrete has basically no insulation value (0.8 concrete compared to 14 of SIPs). So in addition a concrete house will heat up much more than a insulated SIP panel house plus it transfers more heat if air conditioning is used. Concrete is also prone to attract water and so will always have more mold problems in the long run.
From a construction material cost perspective a square meter (m2) of 8 inch block wall reinforced to CR Seismic code will cost about $100/m2 compared to $60/m2 of 4 inch SIP construction panels. So material wise a cinder block wall is about 50% more expensive than a SIP wall! If you take into account that SIPs are 18 times lighter than Block or Concrete substantial cost savings can be achieved in addition by sizing foundations accordingly. In addition usually it takes about 40 hours or more to built a 15m2 block wall according to the seismic code or about 2.6 hours per m2. A SIP construction wall of 15m2 can easily be raised in 5 hours by two people so about 0.3 hours per m2! So again a substantial labour cost advantage of about 800%.
Please see the table below for a 20ft long wall section in 8ft height built in different local construction methods. Material prices are from local Ferreterias (2016) without transport. Labour is a very rough estimate mainly to see the difference between the methods. All Walls are reinforced according to the local earthquake code. That adds especially at the block wall a lot of rebar which has a high cost.
One other major disadvantage concrete walls have is that the plumbing and electric work gets delegated to the local crew on site which is usually not specialized for that type of work in Costa Rica. With SIPs we produce the panels according to a panel plan with the plumbing and electric boxes installed which simplifies field work.
Wall Type Comparison
|Wall Type||Material Cost in $||Labour Cost in $||Total Price Wall in $||Total Weight in KG|
|Concrete Panel Wall||$288||$168||$456||1800 kg|
|Block Wall 20cm||$1307||$216||$1523||7500 kg|
|Block Wall 15cm||$1186||$216||$1402||5625 kg|
|Stick wall 2/6 Pine||$395||$100||$495||410 kg|
|SIP Panel Wall 12cm||$830||$60||$890||290 kg|