When planning a commercial HVAC installation, one of the most important early decisions is choosing the right project delivery method. The two most common approaches are Design-Build and Plan-and-Spec, which offer different advantages depending on your priorities. Design-Build streamlines the process by combining design and construction under one team, often leading to faster timelines and tighter cost control.
Plan-and-Spec separates the design and build phases, offering more upfront cost clarity and design flexibility but requiring more hands-on coordination. Understanding each of the strengths and tradeoffs can help you choose the best fit for your project’s needs.
What is Design-Build?
Design-build simplifies the process by combining both stages into one. The design-build process involves coordination between all parties involved, including the client, contractors and HVAC experts. Unlike traditional methods where design and construction are separate, design-build combines both into one approach. Some of the benefits of choosing Design-Build are:
- Single-Point of Responsibility: One of the biggest advantages of design-build is the single point of responsibility. By combining design and construction, businesses can avoid potential disputes and delays due to miscommunication or conflicting goals between different entities.
- Time and Cost Savings: The design-build process shortens the project timeline since design and construction overlap. With fewer change orders and better communication, decision-making becomes more efficient and saves costs throughout the project.
- Better Collaboration: Collaboration is important to successful project execution. The design-build approach brings all stakeholders together, including clients
What is Plan-and-Spec?
Plan-and-Spec (short for “plans and specifications”) is the more traditional way of tackling an HVAC project. In this setup, an architect or engineer first designs the system, then sends those plans out to different contractors to bid on the installation. The contractor who wins the bid installs the system exactly as it was designed. The design and installation teams usually work under separate contracts, and there’s little to no collaboration between them during the early phases. Some people choose plan-and-spec for the following benefits:
- More design control: The owner or architect is fully in charge of the design before a contractor ever steps in.
- Bidding can lower costs: Because several contractors compete for the job, it can drive installation prices down.
- Everything’s clearly spelled out: Detailed drawings and specs give all bidders the same information, which helps avoid surprises later.
- Checks and balances: With separate contracts, each party is responsible for their own part—design or build—making it easier to assign accountability.
How Does Design-Build and Plan-and-Spec Differ?
Choosing the right project delivery method can have a major impact on how smoothly your build goes—affecting everything from timeline and budget to communication and accountability. Design-build and plan-and-spec take two very different approaches, each with its own strengths and challenges.
1. Ownership and Responsibility
Design-Build gives the client a single point of responsibility. One company handles both the design and the construction, streamlining communication and decision-making.
- One contract, one team, one point of contact.
- If a problem arises, such as a design flaw discovered during construction, the design-builder handles it directly.
- This reduces finger-pointing and helps move things forward faster.
Plan-and-Spec, on the other hand, splits responsibility. The client first hires a designer to complete the plans and then bids out the project to contractors.
- More control over each phase of the project.
- However, it requires the client to act as a go-between, managing two separate teams.
- Design issues discovered during construction can lead to disputes or delays.
2. Team Collaboration
With Design-Build, collaboration starts on day one. Designers and contractors work together as a unified team.
- The team shares a common goal: delivering the best project on time and within budget.
- Adjustments can be made in real time. For example, if material prices spike, the team can quickly redesign or shift the construction plan together.
- This integrated approach fosters better communication and problem-solving.
In Plan-and-Spec, designers and contractors typically work in silos.
- The design team creates plans without input from the construction team.
- Contractors are brought in only after the design is finalized, which can lead to mismatches between design intent and real-world execution.
- Any disconnects have to be resolved after the fact, sometimes causing friction or added costs.
3. Timeline and Efficiency
Design-Build often leads to faster project delivery.
- Because design and construction overlap, work can begin before the design is fully complete (e.g., site prep or foundation work).
- Early coordination helps flag issues before they become costly problems.
- This streamlined process can save weeks or even months on a project.
Plan-and-Spec follows a more traditional, linear timeline:
- The design must be 100% complete before the bidding and construction phases can start.
- While this adds time upfront, it allows for highly detailed planning and a clearer understanding of costs before any construction begins.
4. Risk and Accountability
With Design-Build, most of the risk stays with the design-builder.
- Since one entity is responsible for everything, they’re fully accountable for both the quality of the design and the construction.
- If something goes wrong, the client doesn’t have to figure out who’s to blame.
Plan-and-Spec spreads the risk between multiple parties:
- Design errors fall on the architect or engineer.
- Construction issues are the contractor’s responsibility.
- But when problems span both phases, the client can get stuck in the middle trying to sort it out.
With plan spec, risks are split between the designer and contractor. This can lead to disputes if problems occur. For example, if a construction error is due to a design oversight, the client may have to mediate between the two parties to determine who’s at fault. This division of responsibility adds complexity and stress for the client.
Design-build thrives on collaboration. Everyone works under the same contract, so communication is direct and streamlined. This teamwork reduces misunderstandings and ensures decisions align with the project goals. For example, design choices can be made with real-time input from the construction team, resulting in practical and cost-effective solutions.
Advantages of Design-Build for HVAC Projects
This approach ensures replacement parts and services are available faster. One of the main benefits of design-build is the system is tailored to your building’s exact needs. Whether your space has specific zoning requirements, unique ventilation needs or variable temperature demands, the system will be designed to meet those challenges.
Energy efficiency is necessary for any business. A custom system can improve energy use, lower your utility bills and increase your building’s sustainability. Unlike generic systems, which may be too small or too large for your space, a custom system ensures the equipment is the right size for the building. This means the system won’t be overworked during peak usage periods and won’t waste energy when the building is less occupied.
Comfort is a priority in any commercial space. With a design-build system, you can ensure every area of your building gets the right level of heating, cooling and ventilation. This means fewer hot and cold spots, better air quality and a more pleasant environment for employees, clients and visitors.
Custom-designed systems are easier to maintain because they are built with the specific needs of the building in mind. This means fewer breakdowns, less repairs and lower maintenance costs over the life of the system. Plus a design-build approach ensures replacement parts and services are available, reducing downtime and minimizing disruption to your business.
Plan-and-Spec for HVAC Projects
One of the main reasons an owner will go with a plan and spec is that there is more structure to the construction costs. Once the design stage is complete, the construction documents can then be sent out to the relevant contractors for bidding. This involves each contractor receiving the design drawings and putting together their price for their part of the job and sending this back to the owner.
Once all bids are received, the owner can evaluate how much the overall job will cost and if any reductions need to be made in any areas or if it’s coming in under budget. At least they will get a rough idea of what the price will be to build the building and then decisions can be made on how to proceed.
Plan and Spec also allows for better communication and collaboration between the various teams involved in any given project. No matter what the design discipline, every designer can reach out to each other and work towards the best design.
As the construction teams aren’t waiting on the designs, the design team isn’t limited in the number of solutions they can come up with for design issues. The whole design can be changed if needed and construction isn’t affected in the slightest, as the construction teams haven’t even seen the drawings yet. If the project is unique and there are a lot of things done for the first time, then the plan and spec are perfect for a specialty project like that.
The tricky designs can be tackled head-on without any pressure from contractors. These specialty projects can include intricate architectural designs or a net-zero building.
Potential Pitfalls of Each Approach
No project delivery method is perfect, each comes with its own set of obstacles. Whether you’re pursuing design-build or plan-and-spec, understanding the challenges upfront can help you prepare and make smarter decisions throughout the construction process. Let’s take a closer look at what can go wrong with each approach.
Design-Build Challenges
While design-build has many benefits, it’s important to understand and address the challenges. Some top factors to consider:
- Clear Communication: Communication throughout the project between the client, HVAC specialists and construction teams is important for success.
- Integrating Technology: Embracing technology, such as Building Information Modeling (BIM) software, can greatly improve collaboration and efficiency during the design-build process.
- Compliance with Codes and Regulations: Keeping up to date with local codes and regulations ensures compliance and eliminates complications during inspections and approvals.
Plan-and-Spec Challenges
Plan-and-spec offers more control during design but can present challenges during construction. Top considerations include:
- Pricing Pressure: Contractors bid a fixed price before starting, risking profit loss if issues arise.
- Longer Timelines: The linear process can lead to extended project durations.
- Lowest Bid Wins: Choosing the cheapest contractor can impact quality.
- Communication Gaps: Lack of collaboration between design and construction teams can cause delays and confusion.
Which Approach Should You Choose?
When to Choose Design-Build
Opt for the design-build approach when you want a dedicated, unified team overseeing your project from start to finish. With this method, you’re bringing together experts who’ve handled similar challenges and can seamlessly design and build your HVAC system.
- Expertise: A design-build team has the experience to create tailored solutions, from accurately measuring your building’s square footage to designing efficient heating, cooling, and ventilation systems.
- Efficiency: With both design and construction in one team, you’ll avoid delays and unexpected costs, as they’re responsible for meeting both timelines and budgets.
- Accountability: The design-build team manages the entire project, making sure everyone stays on track and the work is completed on time and within budget.
If you need a reliable, coordinated team that handles all aspects of your HVAC project, design-build is your best choice.
When to Choose Plan-and-Spec
Plan-and-spec is ideal for those who want a more hands-on approach, giving them control over the design and construction phases. In this method, an HVAC design firm will measure your facility and deliver detailed CAD drawings and equipment lists, after which you can solicit bids from contractors.
- Clarity and Control: You get a clearer picture of project costs and design specifications before starting construction.
- Flexibility: Changes to the design can be made in the planning phase, and specialized projects can be better accommodated.
- Cost Management: With separate contracts for design and construction, you can shop around for competitive bids and negotiate project terms.
However, plan-and-spec requires more involvement from the facility manager to coordinate between designers, contractors, and subcontractors. If you have time to manage this coordination and prefer more transparency in pricing, plan-and-spec could be the right choice.
Hybrid Approach: Combining Design-Build and Plan-and-Spec
Combining Design-Build (DB) and Plan-and-Spec (also known as Design-Bid-Build) can be tricky but it’s possible and can offer flexibility in project delivery. Some of the Design-Bid-Build options include:
- Hybrid Contracting: In this model, portions of the project could be delivered via Design-Build while other parts are handled under Plan-and-Spec. For example:
- Design-Build for Complex or Fast-Track: Components including parts of the project that require specialized expertise or need to be completed quickly. Plan-and-Spec for less complex components. For areas of the project that are more straightforward, such as standard building systems or typical elements.
- Phased Delivery: Another option is to combine these methods in a phased approach. The project could start with a Plan-and-Spec design but once the design reaches a certain point the owner could switch to a Design-Build approach for construction or for specific phases. This would allow the owner to get the benefits of each system at different stages of the project.
- Early Contractor Involvement (ECI): In this model the owner starts with a Plan-and-Spec design process but involves the contractor early on to provide input on construction methods, materials and cost estimates. This brings some Design-Build characteristics (collaboration and input from construction early on) into the traditional Plan-and-Spec system. The contractor can help refine the design which may make the final bidding process smoother and potentially more cost effective.
- Design-Build with Plan-and-Spec Additions: In some cases a Design-Build contractor might be tasked with the majority of the work but the owner could opt to issue some specific Plan-and-Spec documents for particular items or systems that require more specialized attention or a more traditional procurement process.
- Multiple Contracts with Overlap: A more complex version could be multiple contracts where the Design-Build contractor is responsible for the main scope of work but subcontractors work under separate Plan-and-Spec contracts for specialized systems or services (e.g. specialized mechanical or electrical systems).
It’s important to define who assumes risk in each model. A hybrid approach should specify which party (owner, contractor or designer) is responsible for various aspects of the design and construction. Combining both methods requires strong coordination, especially if multiple entities are involved. Clear communication and defined project goals are important to any business.
One of the main benefits of Design-Build is fast-tracking; however, introducing Plan-and-Spec elements could delay the project. Make sure to align timelines and understand the impact on the budget. When combining these approaches, the contracts must be carefully written to ensure clarity on the roles and responsibilities of each party.
Contact Unitemp Today for Your HVAC Project Needs
In short, combining Design-Build and Plan-and-Spec allows for flexibility and can leverage the benefits of both systems but it requires careful planning and management to make it work.
Unitemp has a team of designers, engineers and support staff to provide complete consultative services to help you achieve your goals in renovating or installing new HVAC systems. Call 877.704.4822 for a consultation on your facility needs.