My personal workshop is out in a sparsely populated area and I visit it on the weekends.  This past weekend showed signs of someone having entered my property that should not have been there (tire tracks, gate jumper, tracks, etc.).  So time to install an alarm system with siren, strobe, etc.  This is a commerical grade metal building, with 4 - 12'x14' overhead commercial garage doors and one metal entry door.  There are no windows in the building.  It is 60'W x 50'D x 20'H and insulated with R20.  

I plan to use an ELK M1 Gold (little overkill, but I have my reasons) for this setup with an HAI C3 Cellular comm Center (I don't have a hardline out there). I plan on arming all the doors with hardwired switches.  

I am trying to determine how to best protect against someone unscrewing the metal panels and getting in without triping a hardwire zone.  I'm a little concerned about PIR's due to the Texas heat with no heating or cooling in the building. I have looked at some of the OPTEX products, but since I have never used perimeter sensors I don't know what would be best for this configuration.  Not sure if I want to put sensors outside or not, I have some neigbors that have animals (dogs, goats, etc.).  So a little confused on what the best options would be to detect intruders/unwanted vistors.....

Any help or advice is gladly appreciated.
Michael

An alternative would be to purchase a DVR and a few cameras.  The DVR can detect motion as good as a PIR and can also receive inputs from other sensors.  The DVR can connect to the internet and would be fully controllable from a remote location.  You can get notified when an alarm is triggered and then play back the recorded video remotely.  Newer models can interface with an iphone along with the usual computer.  A DVR and 4 cameras can be purchased for around $500.  The recorded video would be much better for determining what happened and perhaps ID who was responsible.

I agree with the suggestion of the DVR as well. Be careful to choose the proper cameras for your environment so that you can obtain the most visual detail you can afford in order to assist the proper authorities. In addition to the DVR triggering a recording or connecting sensors directly to it you can have the cameras upon motion sensing trigger an alarm condition on your security panel of choice. Nice thing here is to set a few random blocks on each of the cameras field of view for the motion thus avoiding a trigger by an animal.

As for sensors, IR beams are a good measure for for perimeter in a large space. As another option consider looking at a Dual Tech Sensor. These are a combination typically of Microwave and PIR and in order to go into alarm they require both to be tripped. They work really nice in commercial environments where you have large space heaters and possible moving apparatus and rodents and greatly reduce if not eliminate false alarms.

The PIRs have a lot of intelligence and require motion across at least 2 sectors before they will trip so having stationary objects gradually heat up and cool should not trip them.  False alerts should not be a problem indoors especially since you have no windows.

I have four Optex PIRs and any movement by even small animals (rabbits, squirrels) and birds flying close by will trip them.  But, they are quite immuned to the natural environment such as various sun angles and wind blowing branches and bushes nearby.

All DVRs have a spec for working temp.  I checked several and the lowest I saw was 40*C (104* F) and even saw some as high as 50*C (122*F).  The ones I have used do not run very hot, just one large circuit board.