| A-1 Plumbing, LLC |
| Arden Lighting Group LLC |
| AB Home Improvement |
| Accurate Electric LLC |
| Anderson Plumbing, LLC |
| Ball Excavation & Plumbing |
| Chas W. Goering Plumbing & Heating |
| D & L Plumbing |
| Dohrmann Plumbing & Heating, Inc. |
| Estes Construction |
| Green's Quality Plumbing, Inc. |
| Gritters Electric |
| H & J Heating and Cooling |
| Harden Brothers Propane |
| HM Cragg |
| Iowa State University |
| KAAS Electric, Inc. |
| Lohrmann Electric |
| Lux Electric |
| Massner Electric, Inc. |
| Milwaukee Tool |
| Moose Mechanical |
| Northwood Electric, Inc. |
| Osceola Foods, Inc. |
| Pac-Van Inc. |
| Pizano Electric, Inc. |
| Priority Plumbing |
| Progressive Foundry, Inc. |
| RT Moore Co., Inc. |
| Redwood Construction |
| Rochon Corporation of Iowa |
| S & S Electric LTD. |
| Sabre Plumbing |
| Schoessler Electric, Inc. |
| Spectrum Lighting & Electric |
| Suter Services |
| Switch Electric |
| The Dana Company |
| Timm Electric, Inc. |
| Total Connection Electric, Inc |
| United Rentals - Trench Safety |
| Walstra Plumbing & Heating |
| Wiremann Electric |